Exchange bias behaviour of amorphous CoFeNiSiB ribbons

Abstract

A dramatic exchange bias behaviour was found in superior soft Co58Fe5Ni10Si11B16 amorphous ribbons with proper thermomagnetic annealing conditions. This characteristic, which was directly obtained at room temperature, is quite different from that of the traditional ferromagnetic–antiferromagnetic system. The observation of microstructure indicated that the matrix of the annealed ribbons with the exchange bias behaviour includes a few crystalline phases. The magnetic domains of the ribbon surface were scanned to clarify the configuration of local magnetic moments. A subsequent magnetic torque measurement revealed that unidirectional magnetic anisotropy was induced in the amorphous ribbons with a longitudinal field. The obtained evidence supports our point of view that the local crystalline phases in the ribbons along with the longitudinal thermomagnetic treatment are the key factors in promoting the formation of an exchange bias. A simple phenomenological discussion was developed to expound this interesting behaviour in ribbons.

Giant magnetoelectric effect in self-biased laminates under zero magnetic field

“…11,12 After being magnetized by a dc magnetic bias, these crystalline and oxidized phases can induce a unidirectional magnetic anisotropy in adjacent amorphous Metglas layers. 13,14 Two layers of Metglas and two layers of annealed Metglas both of dimensions 40 mm  5 mm were then epoxied together. After premagnetizing with a bias of H dc ¼ þ2 kOe, the M-H hysteresis loops were measured by a vibrating sample magnetometer (VSM).…”

Modulation of unidirectional anisotropy for Co-based amorphous ribbons by longitudinal pulse field

“…20 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions.…”

“…20 The samples with EB characteristics were obtained by applying dc magnetic field of 800 A/m along the longitudinal direction of ribbons during annealing. 20 After that, a longitudinal pulse field, which is reverse to annealing field, was applied on the samples with one pulse per 5 s. The surface magnetic domains were scanned by Scanning Probe Microscope (SPM). The modulation of unidirectional anisotropy was exhibited by the measurement of vector vibrating sample magnetometer (VVSM) and simple theoretical calculation.…”

“…[16][17][18] The local crystalline phase, which is magnetically harder than the amorphous matrix, was considered to play a main role in the loop shift in ribbons. 19,20 In this article, we observe the dependence of asymmetrical loops on the longitudinal pulse field for field annealed amorphous ribbons. Surface domains and fieldinduced anisotropy were investigated to reveal the impact of the pulse field on the EB in ribbons.…”

Self-Biased Magnetoelectric Composites: An Overview and Future Perspectives

“…After premagnetizing in a DC saturation field, the low field hysteresis loop shifts are ascribed to the local unidirectional stray field generated by the uncompensated poles at the magnetic harder particles/layer in the soft amorphous matrix/core. Usually, this biphase system can be realized by either partial crystallization of the metallic glass via annealing (Rivas et al 2005;He et al 2009;Zhou et al 2009) or by depositing a hard magnetic outer shell onto the amorphous ribbons (Torrejon et al 2007). …”