Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/014
P. Genoud, Ashutosh Kumar Singh, A. Manuel, T. Jarlborg, E. Walker, M. Peter, M. Weller
The authors report the first study of the Fermi surface topology, electron momentum density and spin momentum density in ferromagnetic iron using two-dimensional angular correlation of polarised positron annihilation radiation. A calculation made in the independent-particle model was obtained from the self-consistent linear muffin-tin orbital method. Comparison between experiment and calculation reveals marked discrepancies which are due to both electron-electron and electron-positron correlation effects. Analysis of experimental distributions shows that the large N-centred hole pocket of minority third band does not exist in contrast with the self-consistent calculation results. A parametrised band-structure calculation has been performed to account for the electron-electron correlation effects. Distributions resulting from this procedure were in better agreement with experiment than the self-consistent ones. Once again the nature of electron-positron correlation effects is found to resemble those observed by Sing et al. for nickel. This confirms the systematic trends of electron-positron correlation effects for localised d electrons. The correct description of the relative spin momentum density distribution requires different enhancement factors for majority and minority electron bands.
{"title":"Electron momentum distribution and spin density of ferromagnetic iron studied by spin-polarised positron annihilation","authors":"P. Genoud, Ashutosh Kumar Singh, A. Manuel, T. Jarlborg, E. Walker, M. Peter, M. Weller","doi":"10.1088/0305-4608/18/9/014","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/014","url":null,"abstract":"The authors report the first study of the Fermi surface topology, electron momentum density and spin momentum density in ferromagnetic iron using two-dimensional angular correlation of polarised positron annihilation radiation. A calculation made in the independent-particle model was obtained from the self-consistent linear muffin-tin orbital method. Comparison between experiment and calculation reveals marked discrepancies which are due to both electron-electron and electron-positron correlation effects. Analysis of experimental distributions shows that the large N-centred hole pocket of minority third band does not exist in contrast with the self-consistent calculation results. A parametrised band-structure calculation has been performed to account for the electron-electron correlation effects. Distributions resulting from this procedure were in better agreement with experiment than the self-consistent ones. Once again the nature of electron-positron correlation effects is found to resemble those observed by Sing et al. for nickel. This confirms the systematic trends of electron-positron correlation effects for localised d electrons. The correct description of the relative spin momentum density distribution requires different enhancement factors for majority and minority electron bands.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"1 1","pages":"1933-1947"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88578337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/026
S. Kaul
With a view to resolving the controversy (see Kaul, 1987; Fish and Rhyne, 1987) surrounding the nature of the magnetic transition. Tc in amorphous (a-)Fe100-xZrx alloys with x=8, 9, 10, published magnetisation data on a-Fe92Zr8 and a-Fe91Zr9 alloys have been reanalysed and detailed bulk magnetisation measurements in the critical region have been performed on a-Fe90Zr10. Other workers have claimed that the critical exponents for spontaneous magnetisation, initial susceptibility and critical isotherm, i.e. beta , gamma and delta , respectively, have anomalously large values for a-Fe92Zr8 and a-Fe90Zr10 alloys, but the authors' data analysis demonstrates that for all the glassy alloys in question the critical exponents beta , gamma and delta possess values that are very close to the three-dimensional Heisenberg values and obey the Widom scaling relation, beta delta = beta + gamma . Consistent with this result, magnetisation data in the critical region do satisfy the magnetic equation of state characteristic of a second-order phase transition. A coherent explanation has been provided for the seemingly contradictory neutron diffraction and magnetisation results within the framework of a model previously proposed by the author. Moreover, recently published thermoelectric power and electrical resistivity data on a-Fe90Zr10 and a-Fe92Zr8, respectively, have also been discussed in the light of the present findings.
{"title":"On the ferromagnetic-paramagnetic phase transition in amorphous iron-rich Fe100-xZrx (x=8, 9, 10) alloys","authors":"S. Kaul","doi":"10.1088/0305-4608/18/9/026","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/026","url":null,"abstract":"With a view to resolving the controversy (see Kaul, 1987; Fish and Rhyne, 1987) surrounding the nature of the magnetic transition. Tc in amorphous (a-)Fe100-xZrx alloys with x=8, 9, 10, published magnetisation data on a-Fe92Zr8 and a-Fe91Zr9 alloys have been reanalysed and detailed bulk magnetisation measurements in the critical region have been performed on a-Fe90Zr10. Other workers have claimed that the critical exponents for spontaneous magnetisation, initial susceptibility and critical isotherm, i.e. beta , gamma and delta , respectively, have anomalously large values for a-Fe92Zr8 and a-Fe90Zr10 alloys, but the authors' data analysis demonstrates that for all the glassy alloys in question the critical exponents beta , gamma and delta possess values that are very close to the three-dimensional Heisenberg values and obey the Widom scaling relation, beta delta = beta + gamma . Consistent with this result, magnetisation data in the critical region do satisfy the magnetic equation of state characteristic of a second-order phase transition. A coherent explanation has been provided for the seemingly contradictory neutron diffraction and magnetisation results within the framework of a model previously proposed by the author. Moreover, recently published thermoelectric power and electrical resistivity data on a-Fe90Zr10 and a-Fe92Zr8, respectively, have also been discussed in the light of the present findings.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"112 1","pages":"2089-2100"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80710526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/007
M. Elliott, M. Harris, M. Podesta
The authors discuss the high-field torque measurements made by Coulter and Datars (1980, 1985). A possible explanation of the measurements in terms of frictional effects is described. The consequences for the CDW model of potassium are outlined.
{"title":"Re-examination of induced-torque measurements in potassium","authors":"M. Elliott, M. Harris, M. Podesta","doi":"10.1088/0305-4608/18/9/007","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/007","url":null,"abstract":"The authors discuss the high-field torque measurements made by Coulter and Datars (1980, 1985). A possible explanation of the measurements in terms of frictional effects is described. The consequences for the CDW model of potassium are outlined.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82810823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/008
H. L. Alberts, J. Lourens
Measurements of the temperature dependence of the elastic moduli and the thermal expansion of two Cr-Ru alloys containing 0.3 and 0.5 at.% Ru are reported. In addition to anomalies at the transition from the incommensurate (I) to the commensurate (C) phase and from C to the paramagnetic phase in both the thermal expansion coefficient and the bulk modulus a new anomaly in the shear modulus has been observed at TIC. Existing itinerant electron theories have been applied to analyse the data. In particular (1/TN)d2TN/d gamma 2, where gamma is the shear strain and TN the Neel temperature has been found to be (13+or-3) and (11+or-3) for the 0.3 and 0.5 at.% Ru alloys respectively.
{"title":"The effect of the incommensurate-commensurate SDW transition on the magnetoelasticity of dilute Cr-Ru alloys","authors":"H. L. Alberts, J. Lourens","doi":"10.1088/0305-4608/18/9/008","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/008","url":null,"abstract":"Measurements of the temperature dependence of the elastic moduli and the thermal expansion of two Cr-Ru alloys containing 0.3 and 0.5 at.% Ru are reported. In addition to anomalies at the transition from the incommensurate (I) to the commensurate (C) phase and from C to the paramagnetic phase in both the thermal expansion coefficient and the bulk modulus a new anomaly in the shear modulus has been observed at TIC. Existing itinerant electron theories have been applied to analyse the data. In particular (1/TN)d2TN/d gamma 2, where gamma is the shear strain and TN the Neel temperature has been found to be (13+or-3) and (11+or-3) for the 0.3 and 0.5 at.% Ru alloys respectively.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76853146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/019
I. Sakamoto, K. Yonemitsu, K. Sato, U. Mizutani
For pt.I see ibid., vol.18, p.1995 (1988). The Hall coefficient RH has been measured for a series of (Ag0.5Cu0.5)1-xGex amorphous alloys in the temperature range 1.5-300 K. The value of RH for x=0.2 is temperature independent over the whole temperature range, whereas that for x=0.5, 0.6 and 0.7 exhibits a T1/2 temperature dependence below about 50 K. The temperature-independent Hall coefficient can be taken as evidence for the negligible contribution of the quantum corrections, lending support to the analysis based on the Boltzmann-type ordinary scattering mechanism for the low-resistivity data in the preceding paper. On the other hand, the square-root temperature dependence of the Hall coefficient provides clear evidence for the dominant role of the electron-electron interaction in high-resistivity alloys.
{"title":"Interplay of the Boltzmann-type ordinary transport and quantum corrections in Ag-Cu-Ge amorphous alloy system. II. Temperature dependence of Hall coefficient","authors":"I. Sakamoto, K. Yonemitsu, K. Sato, U. Mizutani","doi":"10.1088/0305-4608/18/9/019","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/019","url":null,"abstract":"For pt.I see ibid., vol.18, p.1995 (1988). The Hall coefficient RH has been measured for a series of (Ag0.5Cu0.5)1-xGex amorphous alloys in the temperature range 1.5-300 K. The value of RH for x=0.2 is temperature independent over the whole temperature range, whereas that for x=0.5, 0.6 and 0.7 exhibits a T1/2 temperature dependence below about 50 K. The temperature-independent Hall coefficient can be taken as evidence for the negligible contribution of the quantum corrections, lending support to the analysis based on the Boltzmann-type ordinary scattering mechanism for the low-resistivity data in the preceding paper. On the other hand, the square-root temperature dependence of the Hall coefficient provides clear evidence for the dominant role of the electron-electron interaction in high-resistivity alloys.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"18 1","pages":"2009-2014"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79130267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/005
C. P. Flynn
It is shown why the epitaxial growth of high quality metallic superlattices generally requires a growth temperature approximately 3Tm/8 and two components having similar melting temperatures Tm. A general observation of RHEED oscillations from growing metal surfaces at temperatures approximately Tm/8 is also predicted.
{"title":"Constraints on the growth of metallic superlattices","authors":"C. P. Flynn","doi":"10.1088/0305-4608/18/9/005","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/005","url":null,"abstract":"It is shown why the epitaxial growth of high quality metallic superlattices generally requires a growth temperature approximately 3Tm/8 and two components having similar melting temperatures Tm. A general observation of RHEED oscillations from growing metal surfaces at temperatures approximately Tm/8 is also predicted.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80019075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/016
I. Verma, R. Fletcher
Single crystals of lead have been subjected to plastic strain at low temperatures and the resulting effects on the high-field transport properties have been studied. The increase in elastic electronic scattering is pronounced and correlates well with the flow stress, except at the lowest stress values. The high-field electronic thermal resistivity is shown to obey an appropriate Matthiessen's rule, in contrast to the situation that is usually found at zero field. The lattice thermal conductivity is not noticeably affected by the strain, a result consistent with calculations but contrary to the data obtained recently on pure K (Fletcher, Phys. Rev. vol.36, p.3042, 1987). With higher magnetic fields the present techniques might provide a useful alternative to those already in existence in studying phonon-dislocation effects.
{"title":"The effect of plastic strain on the high-field transport properties of Pb","authors":"I. Verma, R. Fletcher","doi":"10.1088/0305-4608/18/9/016","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/016","url":null,"abstract":"Single crystals of lead have been subjected to plastic strain at low temperatures and the resulting effects on the high-field transport properties have been studied. The increase in elastic electronic scattering is pronounced and correlates well with the flow stress, except at the lowest stress values. The high-field electronic thermal resistivity is shown to obey an appropriate Matthiessen's rule, in contrast to the situation that is usually found at zero field. The lattice thermal conductivity is not noticeably affected by the strain, a result consistent with calculations but contrary to the data obtained recently on pure K (Fletcher, Phys. Rev. vol.36, p.3042, 1987). With higher magnetic fields the present techniques might provide a useful alternative to those already in existence in studying phonon-dislocation effects.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"14 1","pages":"1965-1977"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85498046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/015
M. Khalid, P. Reinders, M. Springford
The many-body theory of the de Haas-van Alphen effect of Engelsberg and Simpson (1970) predicts departures from the semiclassical approach of Lifshitz and Kosevich (1956) arising from the influence of the electron-phonon interaction. The magnitude of these departures is calculated for mercury, indium and lead. Accurate measurements of DHVA amplitudes are made for mercury at temperatures between 1.3 and 4.2 K in magnetic fields up to 8 T. Anomalies in the earlier work of Elliot et al. (1978) are re-examined and clarified. The many-body theory is found to be in good quantitative agreement with experiment.
{"title":"A study of the electron-phonon interaction in the de Haas-van Alphen effect","authors":"M. Khalid, P. Reinders, M. Springford","doi":"10.1088/0305-4608/18/9/015","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/015","url":null,"abstract":"The many-body theory of the de Haas-van Alphen effect of Engelsberg and Simpson (1970) predicts departures from the semiclassical approach of Lifshitz and Kosevich (1956) arising from the influence of the electron-phonon interaction. The magnitude of these departures is calculated for mercury, indium and lead. Accurate measurements of DHVA amplitudes are made for mercury at temperatures between 1.3 and 4.2 K in magnetic fields up to 8 T. Anomalies in the earlier work of Elliot et al. (1978) are re-examined and clarified. The many-body theory is found to be in good quantitative agreement with experiment.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"70 1","pages":"1949-1964"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78733602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/020
A. Sheikh
Following the existence of a 'hole' in the local field distribution P(H), the authors have divided the spin system of a spin glass into two groups: those lying at the lower bounds of P(H) are 'effective free' spins and the rest are interacting spins. New expressions for 'effective free' spin populations and interacting spin populations are incorporated into a modified Kondo theory and a spin-diffusion theory respectively. They have thereby obtained a model for magnetic resistivity. The authors analysed experimental data on AgMn, AuMn and CuMn spin glasses, using this model for best fitting of the data. The model gives a satisfactory description of the experimental behaviour for all these alloys. A new resistivity maximum is observed in the interacting spin resistivity at a temperature TSG, close to Tf, the temperature for the AC susceptibility cusp. The temperature Tm, of the resistivity maximum depends on impurity spin S, and it is related to the lower bounds Hc, of P(H).
{"title":"Resistivity of noble-metal-transition-metal spin glasses","authors":"A. Sheikh","doi":"10.1088/0305-4608/18/9/020","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/020","url":null,"abstract":"Following the existence of a 'hole' in the local field distribution P(H), the authors have divided the spin system of a spin glass into two groups: those lying at the lower bounds of P(H) are 'effective free' spins and the rest are interacting spins. New expressions for 'effective free' spin populations and interacting spin populations are incorporated into a modified Kondo theory and a spin-diffusion theory respectively. They have thereby obtained a model for magnetic resistivity. The authors analysed experimental data on AgMn, AuMn and CuMn spin glasses, using this model for best fitting of the data. The model gives a satisfactory description of the experimental behaviour for all these alloys. A new resistivity maximum is observed in the interacting spin resistivity at a temperature TSG, close to Tf, the temperature for the AC susceptibility cusp. The temperature Tm, of the resistivity maximum depends on impurity spin S, and it is related to the lower bounds Hc, of P(H).","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"29 1","pages":"2015-2032"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75757244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1988-09-01DOI: 10.1088/0305-4608/18/9/004
A. Chikdene, A. Baudry, P. Boyer
The diffusive motions of hydrogen in amorphous Zr2NiH2.5 were observed by 181Ta spin relaxation measurements with the perturbed angular correlation (PAC) technique. The temperature dependence of the spin relaxation constant corresponds to an activation energy significantly lower than in the crystallised hydride Zr2NiH3, but does not indicate the existence of a large distribution of hopping rates for the diffusion of hydrogen.
{"title":"Hydrogen diffusion in amorphous Zr2NiH2.5 by 181Ta spin relaxation measurements","authors":"A. Chikdene, A. Baudry, P. Boyer","doi":"10.1088/0305-4608/18/9/004","DOIUrl":"https://doi.org/10.1088/0305-4608/18/9/004","url":null,"abstract":"The diffusive motions of hydrogen in amorphous Zr2NiH2.5 were observed by 181Ta spin relaxation measurements with the perturbed angular correlation (PAC) technique. The temperature dependence of the spin relaxation constant corresponds to an activation energy significantly lower than in the crystallised hydride Zr2NiH3, but does not indicate the existence of a large distribution of hopping rates for the diffusion of hydrogen.","PeriodicalId":16828,"journal":{"name":"Journal of Physics F: Metal Physics","volume":"68 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76567435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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