# Enhancement of thermal stability of Sm(Fe-Co)12-B thin films by cap layer deposition and post-annealing https://mdr.nims.go.jp/datasets/79e22585-20ea-4802-a45c-3f652b6f60a3 ## File - [REPM2025_O13-4_Mori.pdf](https://mdr.nims.go.jp/filesets/c3b92ba2-fcad-4011-9d9c-8fd3b6aac48e/download) ([Detail](https://mdr.nims.go.jp/filesets/c3b92ba2-fcad-4011-9d9c-8fd3b6aac48e.md)) ## Id 79e22585-20ea-4802-a45c-3f652b6f60a3 ## Local identifier ## Visibility open_to_public ## State published ## Created at 2025-08-25T01:39:07.384586Z ## Updated at 2025-09-11T07:30:36.615394Z ## Published at 2025-09-11T07:20:10.447731Z ## Doi https://doi.org/10.48505/nims.5664 ## First published url ## Date published ## Recorded date published ## Resource type conference_presentation ## Manuscript type na ## Collection - id: d28f086a-61aa-4bc7-bcae-5a1078cbc6c7 identifier: https://mdr.nims.go.jp/pid/d28f086a-61aa-4bc7-bcae-5a1078cbc6c7 title: The 28th International Workshop on Rare Earth and Future Permanent Magnets and Their Applications (REPM2025) ## Title - title: Enhancement of thermal stability of Sm(Fe-Co)12-B thin films by cap layer deposition and post-annealing title_type: original lang: en ## Description - description: "SmFe12 compounds with a tetragonal ThMn12-type crystal structure is expected to be a promising candidate for new high-performance permanent magnet materials due to the excellent intrinsic magnetic properties of the Sm(Fe0.8Co0.2)12compound (saturation magnetization: μ0Ms = 1.78 T, anisotropy field: μ0HA = 12 T, and Curie temperature: TC = 879 K) [1]. However, it is well known that the SmFe12 phase is thermo-dynamically unstable in the bulk state, and some Fe sites must be substituted by stabilizing elements such as Al, Ti, V, Co, Nb, and Zr. In addition, it has been reported that a columnar structure in which SmFe12 grains are surrounded by grain boundary phases results in a high coercivity (μ0Hc = 1.2 T) in B-doped Sm(Fe-Co)12 thin films [2], and the coercivity has been successfully increased to 1.8 T by depositing an Al cap layer on Sm(Fe-Co)12-B thin films [3]. Recently, some results have been reported on the improvement of the magnetic properties of Sm-Fe-Co based alloys by the addition of stabilizing elements. For example, the coercivity of Sm-Fe-Co-B-Nb alloys can be increased by enriching Nb and B at the grain boundaries through optimal heat treatment [4]. In addition, it has been reported that partial substitution of Sm sites in Sm(Fe-Co)12 compounds with Zr element increases the saturation magnetization [5]. In this study, in order to further improve the magnetic properties of Sm(Fe0.8Co0.2)12-B thin films, Nb or Zr was deposited as a capping layer on the Sm(Fe-Co)12-B thin films, and then the changes in the crystal structure and magnetic properties by post-annealing at varying annealing temperatures were also investigated in detail.The samples were prepared by using an ultra-high vacuum magnetron sputtering system. First, a V buffer layer with a thickness of 20 nm was deposited on a MgO(100) single crystal substrate at substrate temperature of 400ºC, and then a Sm(Fe-Co)12-B layer of 100 nm was deposited. Subsequently, Nb or Zr cap layer was deposited with varying thicknesses. Then, post annealing was performed at an annealing temperature (Ta) between 400 and 700ºC for 1 h. Finally, a V cover layer of 10 nm was deposited to prevent oxidation. The crystal structure was analyzed by X-ray diffraction (XRD), and the magnetic properties were evaluated by using a superconducting quantum interference device (SQUID) magnetometer.From the XRD patterns, the (002) and (004) peaks of the ThMn12-type crystal structure were clearly observed in Sm(Fe-Co)12-B thin films. The intensity of these peaks was confirmed to decrease when Ta exceeded 500ºC, but was recovered by the deposition of a Nb cap layer. In addition, the peak intensity of the α-Fe phase, which increased at high-temperature annealing, was sufficiently decreased by the deposition of the Nb cap layer. As a result, the coercivity of the film without a cap layer was decreased to 0.09 T at Ta = 600ºC, but the film with the Nb cap layer maintained a high coercivity of approximately 1.0 T even when Ta was increased to 600ºC. Furthermore, in the sample without a cap layer, the easy axis of magnetization varied from perpendicular direction to in-plane direction at Ta = 600ºC, however, by depositing the Nb cap layer, perpendicular magnetic anisotropy was obtained up to Ta = 650ºC. Therefore, it was confirmed that the deposition of a Nb layer as a capping layer improved the thermal stability of Sm(Fe-Co)12-B thin films.\r\n\r\nReferences\r\n[1] Hirayama, Y. K. Takahashi, S. Hirosawa, and K. Hono, Scr. Mater., 138, 62-65 (2017).\r\n[2] Sepehri-Amin, Y. Tamazawa, M. Kambayashi, G. Saito, Y. K. Takahashi, D. Ogawa, T. Ohkubo, S. Hirosawa, M. Doi, T. Shima, and K. Hono: Acta Mater., 194, 337 (2020).\r\n[3] Sepehri-Amin, N. Kulesh, Y. Mori, T. Ohkubo, K. Hono, and T. Shima, Scr. Mater., 242, 115955 (2024).\r\n[4] Kurosawa, M. Matsuura, S. Sakurada, and S. Sugimoto, J. Magn. Magn. Mater., 556, 169414 (2022).\r\n[5] Tozman, Y. K. Takahashi, H. Sepehri-Amin, D. Ogawa, S. Hirosawa, and K. Hono, Acta Mater., 178, 114-121 (2019)." description_type: abstract lang: en ## Creator - name: Yuichi Mori role: author organization: Tohoku Gakuin University, Japan - name: Soga Nakatsuka role: author organization: Tohoku Gakuin University, Japan - name: Masaaki Doi role: author organization: Tohoku Gakuin University, Japan - name: Toshiyuki Shima role: author organization: Tohoku Gakuin University, Japan ## Contact agent ## Publisher organization: National Institute for Materials Science (NIMS) ## Managing organization ## Keyword - subject: REPM2025 schema: not_defined - subject: SmFe12-based compound schema: not_defined - subject: ThMn12-type crystal structure schema: not_defined - subject: Element addition schema: not_defined ## Rights - identifier: https://creativecommons.org/licenses/by/4.0/ ## Other identifier(s) ## Data origin - data_origin_type: other ## Embargo ## Journal ## Conference name: REPM2025 start_date: 2025-07-27 end_date: 2025-07-31 identifier: https://www.nims.go.jp/mmu/repm2025/ ## Related item ## Funding ## Instrument ## Instrument operator ## Instrument managing organization ## Measurement method ## Specimen ## Chemical composition ## Structure for specimen ## Structural feature for specimen ## Specific property for specimen ## Process for specimen treatment ## Computational method ## Energy level/transition state ## Software ## Custom property ## Fileset - id: c3b92ba2-fcad-4011-9d9c-8fd3b6aac48e filename: REPM2025_O13-4_Mori.pdf content_type: application/pdf size: 3851948 md5: 2397697a54660d2240d363b26d5fed2e ## Thumbnail fileset_id: c3b92ba2-fcad-4011-9d9c-8fd3b6aac48e filename: REPM2025_O13-4_Mori.pdf