Experimental and analytical studies were carried out on the magnetocaloric effect (MCE) in the rare-earth alloy of the Laves phase DyAl2, which has the second-order magnetic phase transition (PT) in the region of cryogenic temperatures. The measurements are carried out using an extraction magnetic calorimeter with a Bitter electromagnet. A polycrystalline DyAl2 sample was synthesized followed by heat treatment. X-ray diffraction and elemental chemical analyzes are provided. The magnetization of the sample was measured in magnetic fields up to 13.5 T. Calculations of the entropy changes of the magnetic subsystem ΔSmag are provided. Measurements of the MCEs ΔT − effect in adiabatic and ΔQ − effect in quasi-isothermal conditions were carried out. The MCE investigated by direct method in the temperature range of 15–110 K and magnetic field up to 14 T. It was found that the maximum of the adiabatic MCE in the region of the Curie temperature of the DyAl2 alloy under adiabatic magnetization in a magnetic field of 14 T is ΔT = 12.94 K. The obtained values are well approximated by the , The maximum value of the quasi-isothermal MCE is ΔQ = 3.1 kJ/kg. The value corresponds to the maximum of the entropy change of the magnetic subsystem ΔSmag = 32.3 J/(kg*K). The influence of thermal contact resistance (TCR) on the results of measuring the MCE under quasi-isothermal conditions is assessed.
{"title":"Quasi-isothermal magnetocaloric effect in the DyAl2 alloy in magnetic field up to 14 T","authors":"A.S. Kuznetsov , A.V. Mashirov , I.I. Musabirov , M.S. Anikin , V.I. Mitsiuk , Yu.S. Koshkid’ko , J. Ćwik , A.P. Kamantsev , E.E. Kokorina , K.A. Kolesov , V.G. Shavrov","doi":"10.1016/j.jmmm.2024.172612","DOIUrl":"10.1016/j.jmmm.2024.172612","url":null,"abstract":"<div><div>Experimental and analytical studies were carried out on the magnetocaloric effect (MCE) in the rare-earth alloy of the Laves phase DyAl<sub>2</sub>, which has the second-order magnetic phase transition (PT) in the region of cryogenic temperatures. The measurements are carried out using an extraction magnetic calorimeter with a Bitter electromagnet. A polycrystalline DyAl<sub>2</sub> sample was synthesized followed by heat treatment. X-ray diffraction and elemental chemical analyzes are provided. The magnetization of the sample was measured in magnetic fields up to 13.5<!--> <!-->T. Calculations of the entropy changes of the magnetic subsystem ΔS<sub>mag</sub> are provided. Measurements of the MCEs ΔT − effect in adiabatic and ΔQ − effect in quasi-isothermal conditions were carried out. The MCE investigated by direct method in the temperature range of 15–110 K and magnetic field up to 14 T. It was found that the maximum of the adiabatic MCE in the region of the Curie temperature of the DyAl<sub>2</sub> alloy under adiabatic magnetization in a magnetic field of 14<!--> <!-->T is ΔT = 12.94<!--> <!-->K. The obtained values are well approximated by the <span><math><mrow><mi>Δ</mi><mi>T</mi><mo>∼</mo><mi>Δ</mi><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn><mo>/</mo><mn>3</mn></mrow></msup></mrow></math></span>, The maximum value of the quasi-isothermal MCE is ΔQ = 3.1<!--> <!-->kJ/kg. The value corresponds to the maximum of the entropy change of the magnetic subsystem ΔS<sub>mag</sub> = 32.3<!--> <!-->J/(kg*K). The influence of thermal contact resistance (TCR) on the results of measuring the MCE under quasi-isothermal conditions is assessed.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172612"},"PeriodicalIF":2.5,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Absorption and magnetic circular dichroism (MCD) spectra have been studied in the region of 5I8 → 5F2, 5S2, 5F3, and 5F5 absorption bands of the Ho3+ ion and in the region of 4I9/2→4G7/2, 2K13/2, 4S3/2, 4F7/2, 4F5/2 and 2H9/2 absorption bands of the Nd3+ ion in an antiferromagnetic trigonal crystal Ho0.75Nd0.25Fe3(BO3)4 in the temperature range from 5 to 90 K. A qualitative change in the shape of the MCD spectra of Ho3+ ion was revealed during the spin-reorientation transition at TR = 6.9 К. Below TR, in the easy-axis state of the crystal, the MCD spectrum has a shape typical for paramagnets, i.e., it consists of diamagnetic and paramagnetic parts. Just above TR, in the easy-plane state of the crystal, MCD of Ho3+ ion has a spectrum similar to the absorption spectrum, which is typical for the paramagnetic part of the MCD. It was shown, that in the easy-plane state the exchange field of iron, being perpendicular to the external field directed along the C3 axis, quenches the usual paramagnetic and diamagnetic MCD in Ho3+ ion, but creates a condition for the appearance of a large paramagnetic MCD of mixing (B-term). With temperature increasing, the MCD spectrum of Ho3+ ion gradually turns into a spectrum typical for paramagnets with the predominance of the sign-changing diamagnetic part, because the influence of the exchange field decreases. The shape of the MCD spectra of Nd3+ ions are typical for paramagnets but does not change during the reorientation transition in the rest of the crystal. This means that the magnetic moment of the Nd3+ ion does not make a reorientation transition simultaneously with the Fe3+ and Ho3+ ions of the rest of the crystal. This phenomenon is accounted for by a strong local magnetic anisotropy of the Nd3+ ion and by a weak exchange interaction Fe-Nd, which is not enough for rotation of the Nd3+ ion moment synchronously with that of the Fe3+ ion. The magneto-optical properties of neodymium are controlled by the easy-axis anisotropy of neodymium.
{"title":"Magnetic circular dichroism of f-f electron transitions in Ho3+ and Nd3+ ions in antiferromagnetic crystal Ho0.75Nd0.25Fe3(BO3)4 in the region of spin-reorientation transition","authors":"A.V. Malakhovskii, V.V. Sokolov, A.L. Sukhachev, I.A. Gudim","doi":"10.1016/j.jmmm.2024.172613","DOIUrl":"10.1016/j.jmmm.2024.172613","url":null,"abstract":"<div><div>Absorption and magnetic circular dichroism (MCD) spectra have been studied in the region of <sup>5</sup><em>I</em><sub>8</sub> → <sup>5</sup><em>F</em><sub>2</sub>, <sup>5</sup><em>S</em><sub>2</sub>, <sup>5</sup><em>F</em><sub>3</sub>, and <sup>5</sup><em>F</em><sub>5</sub> absorption bands of the Ho<sup>3+</sup> ion and in the region of <sup>4</sup><em>I</em><sub>9/2</sub>→<sup>4</sup><em>G</em><sub>7/2</sub>, <sup>2</sup><em>K</em><sub>13/2</sub>, <sup>4</sup><em>S</em><sub>3/2</sub>, <sup>4</sup><em>F</em><sub>7/2</sub>, <sup>4</sup><em>F</em><sub>5/2</sub> and <sup>2</sup><em>H</em><sub>9/2</sub> absorption bands of the Nd<sup>3+</sup> ion in an antiferromagnetic trigonal crystal Ho<sub>0.75</sub>Nd<sub>0.25</sub>Fe<sub>3</sub>(BO<sub>3</sub>)<sub>4</sub> in the temperature range from 5 to 90 K. A qualitative change in the shape of the MCD spectra of Ho<sup>3+</sup> ion was revealed during the spin-reorientation transition at <em>T</em><sub>R</sub> = 6.9 К. Below <em>T<sub>R</sub></em>, in the easy-axis state of the crystal, the MCD spectrum has a shape typical for paramagnets, i.e., it consists of diamagnetic and paramagnetic parts. Just above <em>T</em><sub>R</sub>, in the easy-plane state of the crystal, MCD of Ho<sup>3+</sup> ion has a spectrum similar to the absorption spectrum, which is typical for the paramagnetic part of the MCD. It was shown, that in the easy-plane state the exchange field of iron, being perpendicular to the external field directed along the <em>C</em><sub>3</sub> axis, quenches the usual paramagnetic and diamagnetic MCD in Ho<sup>3+</sup> ion, but creates a condition for the appearance of a large paramagnetic MCD of mixing (<em>B</em>-term). With temperature increasing, the MCD spectrum of Ho<sup>3+</sup> ion gradually turns into a spectrum typical for paramagnets with the predominance of the sign-changing diamagnetic part, because the influence of the exchange field decreases. The shape of the MCD spectra of Nd<sup>3+</sup> ions are typical for paramagnets but does not change during the reorientation transition in the rest of the crystal. This means that the magnetic moment of the Nd<sup>3+</sup> ion does not make a reorientation transition simultaneously with the Fe<sup>3+</sup> and Ho<sup>3+</sup> ions of the rest of the crystal. This phenomenon is accounted for by a strong local magnetic anisotropy of the Nd<sup>3+</sup> ion and by a weak exchange interaction Fe-Nd, which is not enough for rotation of the Nd<sup>3+</sup> ion moment synchronously with that of the Fe<sup>3+</sup> ion. The magneto-optical properties of neodymium are controlled by the easy-axis anisotropy of neodymium.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172613"},"PeriodicalIF":2.5,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-23DOI: 10.1016/j.jmmm.2024.172605
Roman Atanasov, Marc du Plessis, Razvan Hirian, Rares Bortnic, Gabriela Souca, Iosif Grigore Deac
Polycrystalline Pr0.65-xGdxSr0.35MnO3 (x = 0.01, 0.05, 0.1, 0.2, 0.3) manganites were prepared by conventional solid-state method. Structural analysis has revealed a change in structure with x = 0.2, from Rhombohedral (R-3c) to Orthorhombic (Pbnm) symmetry. Small oxygen deficiency was found in the samples. The electrical measurements revealed typical colossal magnetoresistance (CMR) behavior, with single metal–insulator peak at Tp for all investigated samples. The small polaron hopping (SPH) and variable-range hopping (VRH) models were used to describe the electrical conduction above Tp. Magnetic measurements show an increase in magnetization below the Curie temperature, TC. Values of Tc diminish with increasing Gd3+ content. Isothermal measurements around critical points suggest a possible interaction between the 4f-ions and Mn-sublattice The magnetic critical behavior analysis established the tri-critical mean-field model to be the governing model for the series. Large magnetic entropy change ΔSM at near room temperature (278 K) was exhibited by the x = 0.01 sample at 2.2 J/kgK in μ0ΔH = 1 T and 5.36 J/kgK in μ0ΔH = 4 T. The largest |ΔSM| value was shown by the x = 0.1 sample. The values of the relative cooling power (RCP) and the temperature-averaged entropy change (TEC) increased with substitution qualifying these compounds as magnetocaloric materials.
{"title":"Magnetocaloric effect, magnetotransport and magnetic properties of polycrystalline Pr(0.65-x)GdxSr0.35MnO3 (x ≤ 0.3) compounds","authors":"Roman Atanasov, Marc du Plessis, Razvan Hirian, Rares Bortnic, Gabriela Souca, Iosif Grigore Deac","doi":"10.1016/j.jmmm.2024.172605","DOIUrl":"10.1016/j.jmmm.2024.172605","url":null,"abstract":"<div><div>Polycrystalline Pr<sub>0.65-x</sub>Gd<sub>x</sub>Sr<sub>0.35</sub>MnO<sub>3</sub> (x = 0.01, 0.05, 0.1, 0.2, 0.3) manganites were prepared by conventional solid-state method. Structural analysis has revealed a change in structure with x = 0.2, from Rhombohedral (<em>R-3c</em>) to Orthorhombic (<em>Pbnm</em>) symmetry. Small oxygen deficiency was found in the samples. The electrical measurements revealed typical colossal magnetoresistance (<em>CMR</em>) behavior, with single metal–insulator peak at <em>T<sub>p</sub></em> for all investigated samples. The small polaron hopping (<em>SPH</em>) and variable-range hopping (<em>VRH</em>) models were used to describe the electrical conduction above <em>T<sub>p</sub>.</em> Magnetic measurements show an increase in magnetization below the Curie temperature, <em>T</em><sub>C</sub>. Values of <em>T<sub>c</sub></em> diminish with increasing Gd<sup>3+</sup> content. Isothermal measurements around critical points suggest a possible interaction between the 4f-ions and Mn-sublattice The magnetic critical behavior analysis established the tri-critical mean-field model to be the governing model for the series. Large magnetic entropy change Δ<em>S</em><sub>M</sub> at near room temperature (278 K) was exhibited by the x = 0.01 sample at 2.2 J/kgK in μ<sub>0</sub>Δ<em>H</em> = 1 T and 5.36 J/kgK in μ<sub>0</sub>Δ<em>H</em> = 4 T. The largest <em>|</em>ΔS<sub>M</sub><em>|</em> value was shown by the x = 0.1 sample. The values of the relative cooling power (<em>RCP</em>) and the temperature-averaged entropy change (<em>TEC</em>) increased with substitution qualifying these compounds as magnetocaloric materials.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172605"},"PeriodicalIF":2.5,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-23DOI: 10.1016/j.jmmm.2024.172601
Magdalena Majewicz, Maria Szlawska
A single crystal of UNi2Si2 has been grown by the Czochralski pulling technique. Its physical properties have been studied over a wide range of temperatures and magnetic field strengths. The main aim of the studies was to construct a magnetic phase diagram of the compound in order to verify the hypothesis of the existence of a Lifshitz point in it. Our studies showed that the boundaries between paramagnetic, modulated and uniform magnetic phases do not merge up to 14 T.
通过 Czochralski 拉技术生长出了 UNi2Si2 单晶体。在广泛的温度和磁场强度范围内对其物理性质进行了研究。研究的主要目的是构建该化合物的磁相图，以验证其中存在利夫希茨点的假设。我们的研究表明，顺磁相、调制相和匀磁相之间的边界在 14 T 以下不会合并。
{"title":"Searching for a Lifshitz point in the magnetic phase diagram of UNi2Si2","authors":"Magdalena Majewicz, Maria Szlawska","doi":"10.1016/j.jmmm.2024.172601","DOIUrl":"10.1016/j.jmmm.2024.172601","url":null,"abstract":"<div><div>A single crystal of UNi<sub>2</sub>Si<sub>2</sub> has been grown by the Czochralski pulling technique. Its physical properties have been studied over a wide range of temperatures and magnetic field strengths. The main aim of the studies was to construct a magnetic phase diagram of the compound in order to verify the hypothesis of the existence of a Lifshitz point in it. Our studies showed that the boundaries between paramagnetic, modulated and uniform magnetic phases do not merge up to 14 T.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172601"},"PeriodicalIF":2.5,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-23DOI: 10.1016/j.jmmm.2024.172598
Gwang-Hee Kim
We investigate a Josephson junction where the weak link consists of a nanomagnetic dimer, featuring two large, antiferromagnetically coupled spins under simple easy-axis anisotropy. In this setup, the exchange coupling constant serves as a transverse anisotropy constant, and the quantum tunneling of the magnetization is influenced by the supercurrent, which behaves like an external magnetic field applied along the hard axis. Our results demonstrate that the superconducting current induces non-Kramers freezing and unfreezing of the magnetic moment’s tunneling within a biaxial spin model driven by exchange interaction. We derive an exact expression for the quenching condition caused by the exchange coupling. Additionally, we extend our analysis to tunneling phenomena in two antiferromagnetically or ferromagnetically coupled spins biased by the anisotropic exchange interaction, revealing more varied cases of tunnel splitting.
{"title":"Exchange-biased quantum tunneling of magnetization in a nanomagnetic dimer via a Josephson current","authors":"Gwang-Hee Kim","doi":"10.1016/j.jmmm.2024.172598","DOIUrl":"10.1016/j.jmmm.2024.172598","url":null,"abstract":"<div><div>We investigate a Josephson junction where the weak link consists of a nanomagnetic dimer, featuring two large, antiferromagnetically coupled spins under simple easy-axis anisotropy. In this setup, the exchange coupling constant serves as a transverse anisotropy constant, and the quantum tunneling of the magnetization is influenced by the supercurrent, which behaves like an external magnetic field applied along the hard axis. Our results demonstrate that the superconducting current induces non-Kramers freezing and unfreezing of the magnetic moment’s tunneling within a biaxial spin model driven by exchange interaction. We derive an exact expression for the quenching condition caused by the exchange coupling. Additionally, we extend our analysis to tunneling phenomena in two antiferromagnetically or ferromagnetically coupled spins biased by the anisotropic exchange interaction, revealing more varied cases of tunnel splitting.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172598"},"PeriodicalIF":2.5,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-22DOI: 10.1016/j.jmmm.2024.172611
Faiza Firdous , Saif M.H. Qaid , Abdullah S. Aldwayyan , Abdullah Ahmed Ali Ahmed , Junaid Munir
High-spin polarized magnetic materials might be useful in spintronics applications. The spin-polarized magnetic, optical, electronic and structural attributes of half-Heusler VXPt (X = Br, Se) alloys were theoretically explored and calculated using the WIEN2k code. The ground states of the structures are optimized, and the bulk moduli and lattice constants are computed. The values obtained from the formation energies show their stability. For VBrPt, an energy gap is present in major and minority spin carriers, while for VSePt, major spin carriers exhibit an energy gap and metallic character is seen in minority spin carriers. The band structures are further illustrated deeply through the investigation of density of states. The electron density graphs depict the ionic bonding in both alloys. The magnetic moments are additionally assessed, and the recorded values support the magnetic characteristics of VBrPt and VSePt. The assessment of how the studied alloys react to light is determined by computing various parameters. The imaginary component and absorption coefficient anticipate substantial light absorption within the visible region. The calculated outcomes unveiled the potential of the examined alloys for applications in spintronics.
{"title":"Magneto-electronic and optoelectronic attributes of half-Heusler VXPt (X = Br, Se) alloys: A first-principles study","authors":"Faiza Firdous , Saif M.H. Qaid , Abdullah S. Aldwayyan , Abdullah Ahmed Ali Ahmed , Junaid Munir","doi":"10.1016/j.jmmm.2024.172611","DOIUrl":"10.1016/j.jmmm.2024.172611","url":null,"abstract":"<div><div>High-spin polarized magnetic materials might be useful in spintronics applications. The spin-polarized magnetic, optical, electronic and structural attributes of half-Heusler VXPt (X = Br, Se) alloys were theoretically explored and calculated using the WIEN2k code. The ground states of the structures are optimized, and the bulk moduli and lattice constants are computed. The values obtained from the formation energies show their stability. For VBrPt, an energy gap is present in major and minority spin carriers, while for VSePt, major spin carriers exhibit an energy gap and metallic character is seen in minority spin carriers. The band structures are further illustrated deeply through the investigation of density of states. The electron density graphs depict the ionic bonding in both alloys. The magnetic moments are additionally assessed, and the recorded values support the magnetic characteristics of VBrPt and VSePt. The assessment of how the studied alloys react to light is determined by computing various parameters. The imaginary component and absorption coefficient anticipate substantial light absorption within the visible region. The calculated outcomes unveiled the potential of the examined alloys for applications in spintronics.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172611"},"PeriodicalIF":2.5,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-22DOI: 10.1016/j.jmmm.2024.172606
Lina Jiang , Cuicui Hu , Yang Chen , Fang Tang , Haifeng Chen , Zilu Xia , Yong Fang , Bin Qian , Haicheng Xuan , Zhida Han
The magnetic properties, magnetocaloric effect, and the critical behavior near Curie temperature (TC) were systematically studied in a series of (Gd1-xErx)3Al2 (x = 0, 0.1, 0.2, 0.3) alloys. As the Er content increases, both the TC and lattice constant gradually decrease. The maximum magnetic entropy change and refrigerant capacity remain relatively high, ranging from −5.8 to −8.5J/kg K and 209.0 to 290.8 J/kg respectively, for a field change of 5 T. The critical exponents, derived from the field dependence of magnetic entropy change, conform to scaling theory and are consistent with those obtained using the Kouvel–Fisher method. These findings suggest that the reliability of the obtained critical exponents and imply the presence of long-range exchange interactions in (Gd1-xErx)3Al2 alloys.
系统研究了一系列 (Gd1-xErx)3Al2 (x = 0, 0.1, 0.2, 0.3) 合金的磁性能、磁致效应以及居里温度 (TC) 附近的临界行为。随着 Er 含量的增加，TC 和晶格常数都逐渐降低。磁场变化为 5 T 时，最大磁熵变化和制冷剂容量仍然相对较高，分别为 -5.8 至 -8.5J/kg K 和 209.0 至 290.8 J/kg。这些发现表明所获得的临界指数是可靠的，并暗示了 (Gd1-xErx)3Al2 合金中存在长程交换相互作用。
{"title":"Critical behavior and tunable magnetocaloric effect in (Gd1-xErx)3Al2 alloys","authors":"Lina Jiang , Cuicui Hu , Yang Chen , Fang Tang , Haifeng Chen , Zilu Xia , Yong Fang , Bin Qian , Haicheng Xuan , Zhida Han","doi":"10.1016/j.jmmm.2024.172606","DOIUrl":"10.1016/j.jmmm.2024.172606","url":null,"abstract":"<div><div>The magnetic properties, magnetocaloric effect, and the critical behavior near Curie temperature (<em>T<sub>C</sub></em>) were systematically studied in a series of (Gd<sub>1-</sub><em><sub>x</sub></em>Er<em><sub>x</sub></em>)<sub>3</sub>Al<sub>2</sub> (<em>x</em> = 0, 0.1, 0.2, 0.3) alloys. As the Er content increases, both the <em>T<sub>C</sub></em> and lattice constant gradually decrease. The maximum magnetic entropy change and refrigerant capacity remain relatively high, ranging from −5.8 to −8.5J/kg K and 209.0 to 290.8 J/kg respectively, for a field change of 5 T. The critical exponents, derived from the field dependence of magnetic entropy change, conform to scaling theory and are consistent with those obtained using the Kouvel–Fisher method. These findings suggest that the reliability of the obtained critical exponents and imply the presence of long-range exchange interactions in (Gd<sub>1-</sub><em><sub>x</sub></em>Er<em><sub>x</sub></em>)<sub>3</sub>Al<sub>2</sub> alloys.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172606"},"PeriodicalIF":2.5,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-22DOI: 10.1016/j.jmmm.2024.172590
Bao Zhu , Bingwen Zhou , Ruiduan Lin , Mengnan Lv , Xingguo Zhang
Electromagnetic pollution problems and military stealth technology need to be solved, the development of new wave absorbing materials has been imminent. In this study, reduced graphene oxide@Co (rGO@Co) powder is obtained by alcoholthermal method, afterwards the different contents of rGO@Co powders are also compounded with Fe81.5Si3B9P3C1Cu1Ti1.5 nanocrystalline powder by high-energy ball milling, obtaining rGO@Co/Fe81.5Si3B9P3C1Cu1Ti1.5 nanocrystalline composite powder, and powder morphology, the nuclear layer structure, soft magnetic properties and corresponding absorbing properties of the materials are studied. The research results are that rGO coats Co and Fe-based nanocrystalline of double magnetic cores in the composite powder, which realizes the synergy of the two magnetic cores to enhance the magnetic loss, is also compatible with the dielectric loss of rGO, and also improves the impedance matching. The minimum reflection loss (RLmin) is −44.18 dB, and the maximum effective absorption bandwidth (EAB) is 5.03 GHz in the amorphous nanocrystalline alloy matrix. When the addition of rGO@Co powder is 1 wt%, the RLmin of composite powder is −52.41 dB (3 mm), which is increased by 18.6 %. The EAB is 6.07 GHz (2 mm), which is increased by 20.7 %.
{"title":"Study on microwave absorbing properties of reduced graphene oxide@Co/Fe81.5Si3B9P3C1Cu1Ti1.5 amorphous nanocrystalline composite","authors":"Bao Zhu , Bingwen Zhou , Ruiduan Lin , Mengnan Lv , Xingguo Zhang","doi":"10.1016/j.jmmm.2024.172590","DOIUrl":"10.1016/j.jmmm.2024.172590","url":null,"abstract":"<div><div>Electromagnetic pollution problems and military stealth technology need to be solved, the development of new wave absorbing materials has been imminent. In this study, reduced graphene oxide@Co (rGO@Co) powder is obtained by alcoholthermal method, afterwards the different contents of rGO@Co powders are also compounded with Fe<sub>81.5</sub>Si<sub>3</sub>B<sub>9</sub>P<sub>3</sub>C<sub>1</sub>Cu<sub>1</sub>Ti<sub>1.5</sub> nanocrystalline powder by high-energy ball milling, obtaining rGO@Co/Fe<sub>81.5</sub>Si<sub>3</sub>B<sub>9</sub>P<sub>3</sub>C<sub>1</sub>Cu<sub>1</sub>Ti<sub>1.5</sub> nanocrystalline composite powder, and powder morphology, the nuclear layer structure, soft magnetic properties and corresponding absorbing properties of the materials are studied. The research results are that rGO coats Co and Fe-based nanocrystalline of double magnetic cores in the composite powder, which realizes the synergy of the two magnetic cores to enhance the magnetic loss, is also compatible with the dielectric loss of rGO, and also improves the impedance matching. The minimum reflection loss (<em>RL<sub>min</sub></em>) is −44.18 dB, and the maximum effective absorption bandwidth (EAB) is 5.03 GHz in the amorphous nanocrystalline alloy matrix. When the addition of rGO@Co powder is 1 wt%, the <em>RL<sub>min</sub></em> of composite powder is −52.41 dB (3 mm), which is increased by 18.6 %. The EAB is 6.07 GHz (2 mm), which is increased by 20.7 %.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172590"},"PeriodicalIF":2.5,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Magnetic field annealing-induced grain refinement usually occurs during the crystallization process of amorphous alloys. This work investigates the effects of magnetic field annealing on the microstructure and magnetic properties of crystalline Ce17Fe76Co1Zr0.5B6Mo0.5 alloys. The results indicate that magnetic field annealing below the Curie temperature (TC) of the Ce2Fe14B phase in the alloys reduces the alloy’s grain size. At an annealing temperature of 433 K, the average grain size of alloys decreased from 48.0 nm in the as-spun sample to 27.2 nm in the magnetic field annealing sample. Moreover, magnetic field annealing can effectively reduce the volume fraction of the CeFe2 phase in the alloy. After magnetic field annealing at 433 K, the alloy obtained the optimal comprehensive magnetic properties: the intrinsic coercivity (Hci = 441.1 kA/m), remanence (Br = 0.49 T), squareness (Hk/Hci = 0.53), and maximum energy product ((BH)max) = 35.5 kJ/m3), which were 0.2 %, 16.7 %, 6 %, and 29.1 % higher than the values of the as-spun sample, respectively. Precession electron diffraction (PED) analysis revealed that magnetic field annealing increased strain at grain and phase boundaries and a more uniform grain orientation spread (GOS), promoting recrystallization and grain refinement. This study provides new insights into the grain refinement mechanism of crystalline alloys under magnetic field annealing, contributing to further improving the magnetic properties of Ce-Fe-B magnets.
{"title":"A novel grain refinement of Ce-Fe-B magnets induced by magnetic field annealing","authors":"Kehan Zhang, Zhongxing Mao, Haonan Li, Yubing Xia, Xiaohua Tan, Hui Xu","doi":"10.1016/j.jmmm.2024.172607","DOIUrl":"10.1016/j.jmmm.2024.172607","url":null,"abstract":"<div><div>Magnetic field annealing-induced grain refinement usually occurs during the crystallization process of amorphous alloys. This work investigates the effects of magnetic field annealing on the microstructure and magnetic properties of crystalline Ce<sub>17</sub>Fe<sub>76</sub>Co<sub>1</sub>Zr<sub>0.5</sub>B<sub>6</sub>Mo<sub>0.5</sub> alloys. The results indicate that magnetic field annealing below the Curie temperature (T<sub>C</sub>) of the Ce<sub>2</sub>Fe<sub>14</sub>B phase in the alloys reduces the alloy’s grain size. At an annealing temperature of 433 K, the average grain size of alloys decreased from 48.0 nm in the as-spun sample to 27.2 nm in the magnetic field annealing sample. Moreover, magnetic field annealing can effectively reduce the volume fraction of the CeFe<sub>2</sub> phase in the alloy. After magnetic field annealing at 433 K, the alloy obtained the optimal comprehensive magnetic properties: the intrinsic coercivity (H<sub>ci</sub> = 441.1 kA/m), remanence (B<sub>r</sub> = 0.49 T), squareness (H<sub>k</sub>/H<sub>ci</sub> = 0.53), and maximum energy product ((BH)<sub>max</sub>) = 35.5 kJ/m<sup>3</sup>), which were 0.2 %, 16.7 %, 6 %, and 29.1 % higher than the values of the as-spun sample, respectively. Precession electron diffraction (PED) analysis revealed that magnetic field annealing increased strain at grain and phase boundaries and a more uniform grain orientation spread (GOS), promoting recrystallization and grain refinement. This study provides new insights into the grain refinement mechanism of crystalline alloys under magnetic field annealing, contributing to further improving the magnetic properties of Ce-Fe-B magnets.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172607"},"PeriodicalIF":2.5,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-21DOI: 10.1016/j.jmmm.2024.172603
Shubham Rajput, S.D. Tiwari
Uncoated and oleic acid coated ferrimagnetic particles are synthesized. Both samples contain similar magnetite particles. Structural characterization of these particles is performed using x-ray diffraction, Fourier transform infrared spectra, dynamic light scattering, transmission electron microscopy and thermogravimetric analysis. Average crystallite size of magnetite is 7 nm. Thickness of oleic acid layer on each magnetite particle is 1 nm. The oleic acid coated sample contains 23% oleic acid. Temperature dependence of the zero field cooled susceptibility curve of the uncoated magnetite particles peaks at 120 K. The zero field cooled and the field cooled susceptibility versus temperature curves bifurcate at 195 K. The peak temperature and the bifurcation temperature of the system decrease due to the oleic acid coating. The inverse susceptibility does not vary linearly with temperature in high temperature region. Magnetization versus applied magnetic field data at 250 K are analyzed in different ways to study the interparticle interaction effect on magnetization. We find that the interparticle interactions affect the magnetization process of ferrimagnetic nanoparticles.
合成了无涂层和油酸涂层的铁磁性颗粒。两种样品都含有类似的磁铁矿颗粒。利用 X 射线衍射、傅立叶变换红外光谱、动态光散射、透射电子显微镜和热重分析对这些颗粒进行了结构表征。磁铁矿的平均结晶尺寸为 7 纳米。每个磁铁矿颗粒上的油酸层厚度为 1 纳米。油酸涂层样品含有 23% 的油酸。未涂层磁铁矿颗粒的零场冷却电感曲线随温度变化的峰值在 120 K。在高温区，反磁感应强度并不随温度线性变化。对 250 K 时的磁化率与外加磁场数据进行了不同的分析，以研究粒子间相互作用对磁化率的影响。我们发现，粒子间的相互作用会影响铁磁性纳米粒子的磁化过程。
{"title":"Interparticle interaction effect on superparamagnetic properties of ferrimagnetic particles","authors":"Shubham Rajput, S.D. Tiwari","doi":"10.1016/j.jmmm.2024.172603","DOIUrl":"10.1016/j.jmmm.2024.172603","url":null,"abstract":"<div><div>Uncoated and oleic acid coated ferrimagnetic particles are synthesized. Both samples contain similar magnetite particles. Structural characterization of these particles is performed using x-ray diffraction, Fourier transform infrared spectra, dynamic light scattering, transmission electron microscopy and thermogravimetric analysis. Average crystallite size of magnetite is 7 nm. Thickness of oleic acid layer on each magnetite particle is 1 nm. The oleic acid coated sample contains 23% oleic acid. Temperature dependence of the zero field cooled susceptibility curve of the uncoated magnetite particles peaks at 120 K. The zero field cooled and the field cooled susceptibility versus temperature curves bifurcate at 195 K. The peak temperature and the bifurcation temperature of the system decrease due to the oleic acid coating. The inverse susceptibility does not vary linearly with temperature in high temperature region. Magnetization versus applied magnetic field data at 250 K are analyzed in different ways to study the interparticle interaction effect on magnetization. We find that the interparticle interactions affect the magnetization process of ferrimagnetic nanoparticles.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172603"},"PeriodicalIF":2.5,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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