Asymmetric magnetization reversal in exchange biased polycrystalline F/AF bilayers

This paper describes a model for magnetization reversal in polycrystalline Ferromagnetic/Antiferromagnetic exchange biased bilayers. We assume that the exchange energy can be expanded into cosine power series. We show that it is possible to fit experimental asymmetric shape of hysteresis loops in exchange biased bilayer for any direction of the applied field. The hysteresis asymmetry is discussed in terms of energy considerations. An angle beta is introduced to quantify the easy axis dispersion of AF grains.Comment: 15 pages, 4 figure

Direct and inverse measurement of thin films magnetostriction

Two techniques of measurements of thin film magnetostriction are compared: direct, when changes of the substrate curvature caused by the film magnetization are controlled, and inverse ("indirect"), when the modification of the magnetic anisotropy induced by the substrate deformation (usually bending) is measured. We demonstrate how both the elastic strength of the substrate and the effective magneto-mechanical coupling between the substrate deformation and magnetic anisotropy of the film depend on different conditions of bending. Equations to be used for magnetostriction value determination in typical cases are given and critical parameters for the corresponding approximations are identified.Comment: 13 pages, 10 figures, 1 table, submitted to JMM

Temperature dependence of the exchange bias properties in polycrystalline BiFeO<inf>3</inf>/Ni<inf>80</inf>Fe<inf>20</inf>

cited By 0; Conference of 2015 IEEE International Magnetics Conference, INTERMAG 2015 ; Conference Date: 11 May 2015 Through 15 May 2015; Conference Code:113931International audienceIn this study, we report a temperature dependent analysis of the exchange bias properties in BFO/Py bilayers as a function of the BFO thickness. The temperature dependence of the exchange bias field (He) and the coercive field (Hc) are first presented. To understand exchange bias magnetization reversal and the magnetic anisotropies, we will then present an azimuthal study of He and Hc at 300 K and 77 K. Finally, results of a controlled field cooling protocol applied on all samples will be discussed to understand anisotropy energy distribution. The bilayers were grown by radio-frequency sputter deposition, with the following structure: Si/Pt(14 nm)/BiFeO3(tBFO)/Ni80Fe20(10 nm)/ Pt(10 nm), with tBFO among 0 nm, 29 nm and 177 nm . To induce uniaxial anisotropy, a 300 Oe field Hdep was applied during the growth . The XRD analysis confirmed a single polycrystalline structure for the BFO layer

Experimental evidences and driving mechanisms for anisotropic misalignments in exchange coupled systems

Experimental evidence for misalignments between F anisotropy axes, AF anisotropy axes and the exchange bias field direction is shown in a CoFe/Ni 0.38 O0.62 system. The angular dependence of the remanent magnetization, the exchange bias field and the coercive field is studied as a function of the diluted NiO thickness. The exchange coupling leads to misalignments between the applied field during growth, the exchange bias field and the coercive field directions. It shows that two different interfacial spin frustrations are present, corresponding to pinned and unpinned spins contributions of the diluted NiO. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2011