Pub Date : 2025-08-27DOI: 10.1109/TMAG.2025.3603454
Karthik Bharadwaj;Shayan Srinivasa Garani
We propose an efficient encoding algorithm and architecture for 2-D quasi-cyclic (QC) low-density parity-check (LDPC) codes. The encoding algorithm is derived based on the null space of the parity-check tensor obtained by tiling random permutation tensors satisfying certain girth constraints toward improved error correction performance. Our contributions are threefold. First, the construction of 2-D LDPC codes is generalized to accommodate random tilings of permutation tensors, providing code design flexibility over prior work based on predefined shifts. We provide the conditions for obtaining girth greater than four and six, useful for deriving the parity-check tensor of the code algorithmically. Second, based on the parity-check tensor, the generator tensor of the 2-D code is derived. We prove that the generator tensor of a 2-D code whose parity-check tensor has the same i-shifts within each block row, regardless of the j-shifts, comprises tiles of circulant tensors, useful for hardware realization. Third, three different hardware architectures that trade off hardware resources with speed and throughput are proposed. Finally, we analyze the performance of the code via simulations. The proposed 2-D codes are capable of correcting random errors and cluster errors by design. Specifically, for a 2-D LDPC code of rate 0.5 and size 50 $times$ 100, the proposed approach with random shifts along with layered decoding achieves a 0.7 dB signal-to-noise ratio (SNR) gain for random errors at a code failure rate (CFR) of 10−5 and a 1.8 dB SNR gain for burst errors, compared to non-layered decoding with predefined shifts.
{"title":"Efficient Encoding Algorithm and Architecture for 2-D Quasi-Cyclic LDPC Codes With Applications to 2-D Magnetic Recording","authors":"Karthik Bharadwaj;Shayan Srinivasa Garani","doi":"10.1109/TMAG.2025.3603454","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3603454","url":null,"abstract":"We propose an efficient encoding algorithm and architecture for 2-D quasi-cyclic (QC) low-density parity-check (LDPC) codes. The encoding algorithm is derived based on the null space of the parity-check tensor obtained by tiling random permutation tensors satisfying certain girth constraints toward improved error correction performance. Our contributions are threefold. First, the construction of 2-D LDPC codes is generalized to accommodate random tilings of permutation tensors, providing code design flexibility over prior work based on predefined shifts. We provide the conditions for obtaining girth greater than four and six, useful for deriving the parity-check tensor of the code algorithmically. Second, based on the parity-check tensor, the generator tensor of the 2-D code is derived. We prove that the generator tensor of a 2-D code whose parity-check tensor has the same i-shifts within each block row, regardless of the j-shifts, comprises tiles of circulant tensors, useful for hardware realization. Third, three different hardware architectures that trade off hardware resources with speed and throughput are proposed. Finally, we analyze the performance of the code via simulations. The proposed 2-D codes are capable of correcting random errors and cluster errors by design. Specifically, for a 2-D LDPC code of rate 0.5 and size 50 <inline-formula> <tex-math>$times$ </tex-math></inline-formula> 100, the proposed approach with random shifts along with layered decoding achieves a 0.7 dB signal-to-noise ratio (SNR) gain for random errors at a code failure rate (CFR) of 10−5 and a 1.8 dB SNR gain for burst errors, compared to non-layered decoding with predefined shifts.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"61 11","pages":"1-24"},"PeriodicalIF":1.9,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145455950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-27DOI: 10.1109/TMAG.2025.3597516
{"title":"IEEE Magnetics Society Information","authors":"","doi":"10.1109/TMAG.2025.3597516","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3597516","url":null,"abstract":"","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"61 9","pages":"C2-C2"},"PeriodicalIF":1.9,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11142926","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144909317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-27DOI: 10.1109/TMAG.2025.3597521
{"title":"IEEE Magnetics Society Information","authors":"","doi":"10.1109/TMAG.2025.3597521","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3597521","url":null,"abstract":"","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"61 9","pages":"C2-C2"},"PeriodicalIF":1.9,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11142929","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144909398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-22DOI: 10.1109/TMAG.2025.3601608
Akhila Priya Kotti;Amaresh Chandra Mishra
Integrating different geometries into a single nanostructure paves the way to obtain magnetic properties available in both isolated geometries. Wire and tube nanostructures are among the most explored morphologies in the ferromagnetic cylindrical structure area. This work examines wire–tube heterostructures with the inclusion of bulged and tapered diameter modulations, which enhance the control over static magnetic properties. An extra step is observed in the hysteresis loops corresponding to the switching originated initially in the tube region, followed by the wire region. The pinning of the domain wall at the wire–tube interface can also be observed. Remanent states show that vortex domain walls can be nucleated at the ends along with the interface, depending on the radius and the type of modulation. The core region of the vortex configuration is shifted for low values of radius, resulting in a unique arrangement of spins just before reversal. Angular variation of coercivity dictates that the reversal mechanism follows propagation of domain walls along with rotation to initially switch the spins in the tube region and later in the wire region till a certain critical angle. Later, the entire wire–tube structure shows pseudocoherent rotation. A modified two-phase (MTP) model is formulated to fit the simulated data of angular coercivity below the critical angle. Above the critical angle, the Stoner–Wohlfarth (SW) model fits well with simulated data. It has been demonstrated that in the case of extremely tapered wire–tube structures, the critical angle is almost nonexistent, and the MTP model explains the reversal mechanism at all field inclinations.
{"title":"A Modified Two-Phase Model to Address the Magnetization Reversal Mechanism and Angular Dependence of Coercivity in Conical Wire–Tube Heterostructures","authors":"Akhila Priya Kotti;Amaresh Chandra Mishra","doi":"10.1109/TMAG.2025.3601608","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3601608","url":null,"abstract":"Integrating different geometries into a single nanostructure paves the way to obtain magnetic properties available in both isolated geometries. Wire and tube nanostructures are among the most explored morphologies in the ferromagnetic cylindrical structure area. This work examines wire–tube heterostructures with the inclusion of bulged and tapered diameter modulations, which enhance the control over static magnetic properties. An extra step is observed in the hysteresis loops corresponding to the switching originated initially in the tube region, followed by the wire region. The pinning of the domain wall at the wire–tube interface can also be observed. Remanent states show that vortex domain walls can be nucleated at the ends along with the interface, depending on the radius and the type of modulation. The core region of the vortex configuration is shifted for low values of radius, resulting in a unique arrangement of spins just before reversal. Angular variation of coercivity dictates that the reversal mechanism follows propagation of domain walls along with rotation to initially switch the spins in the tube region and later in the wire region till a certain critical angle. Later, the entire wire–tube structure shows pseudocoherent rotation. A modified two-phase (MTP) model is formulated to fit the simulated data of angular coercivity below the critical angle. Above the critical angle, the Stoner–Wohlfarth (SW) model fits well with simulated data. It has been demonstrated that in the case of extremely tapered wire–tube structures, the critical angle is almost nonexistent, and the MTP model explains the reversal mechanism at all field inclinations.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"61 10","pages":"1-12"},"PeriodicalIF":1.9,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145141761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-21DOI: 10.1109/TMAG.2025.3601525
Siri Narla;Piyush Kumar;Azad Naeemi
In this work, we present a novel non-volatile spin transfer torque (STT)-assisted spin–orbit torque (SOT)-based ternary content addressable memory (TCAM) with five transistors and two magnetic tunnel junctions (MTJs). We perform a comprehensive study of the proposed design from the device level to the application level. At the device level, various write characteristics such as the write error rate, time, and current have been obtained using micromagnetic simulations. The array-level search and write performance have been evaluated based on SPICE circuit simulations with layout extracted parasitics for bit-cells while also accounting for the impact of interconnect parasitics at the 7 nm technology node. A search error rate (SER) of $3.9 times 10 {^{-}11 }$ is projected for exact search while accounting for various sources of variation in the design. In addition, the resolution of the search operation is quantified under various scenarios to understand the achievable quality of the approximate search operations. Application-level performance and accuracy of the proposed design have been evaluated and benchmarked against other state-of-the-art CAM designs in the context of a CAM-based recommendation system.
{"title":"A 5T-2MTJ STT-Assisted Spin-Orbit-Torque-Based Ternary Content Addressable Memory for Hardware Accelerators","authors":"Siri Narla;Piyush Kumar;Azad Naeemi","doi":"10.1109/TMAG.2025.3601525","DOIUrl":"https://doi.org/10.1109/TMAG.2025.3601525","url":null,"abstract":"In this work, we present a novel non-volatile spin transfer torque (STT)-assisted spin–orbit torque (SOT)-based ternary content addressable memory (TCAM) with five transistors and two magnetic tunnel junctions (MTJs). We perform a comprehensive study of the proposed design from the device level to the application level. At the device level, various write characteristics such as the write error rate, time, and current have been obtained using micromagnetic simulations. The array-level search and write performance have been evaluated based on SPICE circuit simulations with layout extracted parasitics for bit-cells while also accounting for the impact of interconnect parasitics at the 7 nm technology node. A search error rate (SER) of <inline-formula> <tex-math>$3.9 times 10 {^{-}11 }$ </tex-math></inline-formula> is projected for exact search while accounting for various sources of variation in the design. In addition, the resolution of the search operation is quantified under various scenarios to understand the achievable quality of the approximate search operations. Application-level performance and accuracy of the proposed design have been evaluated and benchmarked against other state-of-the-art CAM designs in the context of a CAM-based recommendation system.","PeriodicalId":13405,"journal":{"name":"IEEE Transactions on Magnetics","volume":"61 10","pages":"1-9"},"PeriodicalIF":1.9,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145141728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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