Training Effect in an Exchange Bias System: The Role of Interfacial Domain Walls

Thomas Hauet (1) , J.A. Borchers (2) , Ph Mangin (3) , Y Henry (4) , S Mangin (1)

1 IJL - Institut Jean Lamour
2 NIST Center for Neutron Research
3 LLB - UMR 12 - Laboratoire Léon Brillouin
4 IPCMS - Institut de Physique et Chimie des Matériaux de Strasbourg

Polarized neutron reflectivity (PNR) is used to obtain the magnetic depth profile of an antiferromagneti-cally coupled ferrimagnetic/ferrimagnetic bilayer, Gd 40 Fe 60 =Tb 12 Fe 88. This system shows a transition from positive to negative exchange bias field H E as the cooling field H cf is increased from small to large positive value. It also exhibits training behavior upon field cycling which affects H E and the coercive field H C. From the PNR measurements at room temperature and at 15 K, we confirm that the magnetic configuration inside the TbFe layer is frozen when the sample is cooled in various H cf. The thickness and pitch of the magnetic twist inside the TbFe layer depend on H cf and give rise to the observed differences in the bias field. Irreversible reorganization of the TbFe magnetization at the interface occurs upon GdFe magne-tization reversal and is found to explain the training effect as well as the overall reduction in coercivity.

Mots clés: thin films; exchange-bias; ferrimagnetic; neutron reflectivity; amorphous; exchange-spring; magnetometry

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Thomas Hauet, J.A. Borchers, Ph Mangin, Y Henry, S Mangin. Training Effect in an Exchange Bias System: The Role of Interfacial Domain Walls. Physical Review Letters, 2006, ⟨10.1103/PhysRevLett.96.067207⟩. ⟨hal-01345166⟩