Abstract

FERMIN, José R.. Dependence of exchange bias in NiFe/NiO bilayers on film thickness. Rev. mex. fis. [online]. 2017, vol.63, n.2, pp.145-150. ISSN 0035-001X.

Here we report on the effect of the ferromagnetic (FM) and antiferromagnetic (AF) films thicknesses on the exchange bias field in a FM/AF bilayer. For this, a series of NiFe(t NiFe)/NiO(t NiO) bilayers were grown by DC magnetron sputtering onto commercial Si(001) wafers. Magneto-optical hysteresis loops were used as probes to measure the exchange-bias field, and the coercivity field, as functions of the in-plane angle, ${\phi }_H$, and the films’ thicknesses, t NiFe and t NiO. The in-plane symmetry of the exchange field and coercivity display unidirectional and uniaxial anisotropies, with angular dependences different from the simple $\mathrm{c}\mathrm{o}\mathrm{s}{\phi }_H$ and $co{s}^2{\phi }_H$, respectively. These symmetries are intrinsically sensitive to the thickness of both NiFe and NiO layers. With respect to the FM layer thickness, the exchange bias and coercivity field follow the usual 1/t NiFe, while the dependence on the thickness of the AF layer is more complicated, and is characterized by a critical behavior.

Keywords : Exchange-bias; unidirectional anisotropy; NiFe/NiO bilayers; magnetic biasing materials; exchange bias symmetry.

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