Title :
The Origin for Training Effects in Exchange Bias Systems: Frustration and Multiple Anisotropy Axes at the Interface
Author_Institution :
Argonne Nat. Lab., Argonne
Abstract :
The interaction of an antiferromagnet with a ferromagnet can establish a unidirectional anisotropy, which is referred to as an exchange bias. This paper presents a numerical simulations based on a simple coherent rotation model, which imply that the initial irreversibilities observed between the first and second hysteresis loop are driven by the symmetry of the antiferromagnet. The availability of more than one easy axis in a high symmetry antiferromagnet can give rise to a spin-flop transition during the first field reversal, after which the antiferromagnetic spins are trapped in a metastable configuration. The calculations show a very pronounced training effect for the case of antiferromagnets with two anisotropy axes, while no training is observed for antiferromagnets with only one anisotropy axis. This explains quite naturally why training effects are only observed for exchange bias systems with high symmetry antiferromagnets, while they are absent for antiferromagnets with uniaxial anisotropy.
Keywords :
antiferromagnetic materials; exchange interactions (electron); ferromagnetic materials; magnetic anisotropy; magnetic hysteresis; spin systems; antiferromagnet-ferromagnet interaction; antiferromagnetic spins; coherent rotation model; exchange bias systems; hysteresis loop; metastable configuration; multiple anisotropy axes; spin-flop transition; training effects; Anisotropic magnetoresistance; Antiferromagnetic materials; Availability; Cooling; Laboratories; Magnetic hysteresis; Materials science and technology; Metastasis; Micromagnetics; Numerical simulation;
Conference_Titel :
Magnetics Conference, 2006. INTERMAG 2006. IEEE International
Conference_Location :
San Diego, CA
Print_ISBN :
1-4244-1479-2
DOI :
10.1109/INTMAG.2006.376306