Anomalous Hysteresis Behavior in Sputter-deposited Ultrathin Films of Amorphous- CoFeB Alloy

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Main Authors: Ghadai, Baisali, Kirti, Kirti, Mishra, Abinash, Mondal, Sucheta
Format: Preprint
Published: 2025
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_version_ 1866915688239595520
author Ghadai, Baisali
Kirti, Kirti
Mishra, Abinash
Mondal, Sucheta
author_facet Ghadai, Baisali
Kirti, Kirti
Mishra, Abinash
Mondal, Sucheta
contents Thin amorphous-CoFeB (a-CFB) is deposited by rf-magnetron sputtering on a self-oxidized Si (100) substrate with different film thicknesses ranging from 0.7 nm to 20 nm. The 5-nm-thick a-CFB film is capped with a W layer for comparison. The surface morphology is investigated by using the atomic force microscopy technique. The low roughness of all the surface of the film indicates uniformity, moderate corrosion resistance, and good structural quality. The X-ray diffraction spectra reveal the amorphous nature of the CFB layer, while the W capping is of mixed phase in the experimental thickness regime. In-plane and out-of-plane hysteresis loops obtained from the vibrating sample magnetometry technique show a transition from an upright S to nearly rectangular shape via a completely inverted profile. A self-sustained tilted magnetic anisotropy is stabilized in a seed-free environment based on the direct substrate-to-magnet interaction. The interface anisotropy is estimated to be 0.06 erg/cm2. The complex anisotropic behavior originates from the interplay between interface anisotropy, conventional shape anisotropy, growth-induced anisotropies, and inhomogeneity-induced anisotropies. In essence, effective anisotropy is responsible for the anomalous hysteresis behavior observed in these films, and this work might provide valuable insights to improve the functionalities of amorphous soft magnetic alloys.
format Preprint
id arxiv_https___arxiv_org_abs_2512_18316
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Anomalous Hysteresis Behavior in Sputter-deposited Ultrathin Films of Amorphous- CoFeB Alloy
Ghadai, Baisali
Kirti, Kirti
Mishra, Abinash
Mondal, Sucheta
Materials Science
Thin amorphous-CoFeB (a-CFB) is deposited by rf-magnetron sputtering on a self-oxidized Si (100) substrate with different film thicknesses ranging from 0.7 nm to 20 nm. The 5-nm-thick a-CFB film is capped with a W layer for comparison. The surface morphology is investigated by using the atomic force microscopy technique. The low roughness of all the surface of the film indicates uniformity, moderate corrosion resistance, and good structural quality. The X-ray diffraction spectra reveal the amorphous nature of the CFB layer, while the W capping is of mixed phase in the experimental thickness regime. In-plane and out-of-plane hysteresis loops obtained from the vibrating sample magnetometry technique show a transition from an upright S to nearly rectangular shape via a completely inverted profile. A self-sustained tilted magnetic anisotropy is stabilized in a seed-free environment based on the direct substrate-to-magnet interaction. The interface anisotropy is estimated to be 0.06 erg/cm2. The complex anisotropic behavior originates from the interplay between interface anisotropy, conventional shape anisotropy, growth-induced anisotropies, and inhomogeneity-induced anisotropies. In essence, effective anisotropy is responsible for the anomalous hysteresis behavior observed in these films, and this work might provide valuable insights to improve the functionalities of amorphous soft magnetic alloys.
title Anomalous Hysteresis Behavior in Sputter-deposited Ultrathin Films of Amorphous- CoFeB Alloy
topic Materials Science
url https://arxiv.org/abs/2512.18316