Surface magneto-optical Kerr effect for ultrathin Ni-Fe bilayers

Abstract

Surface magneto-optical Kerr effect is used to measure magnetic hysteresis loops for Ni-Fe bilayers previously studied by ferromagnetic resonance [Phys. Rev. 38, 12879 (1988)]. The approach to saturation in the [11] direction confirms the existence of enhanced fourfold in-plane magnetic anisotropy, attributed to the effect of arrays of misfit dislocations arising during the epitaxial growth of bcc Ni overlayers on ultrathin layers of bcc (001)Fe. The [11] magnetization curves for 10 monolayers (ML) of Ni on 7 ML of Fe shows a breaking of symmetry between positive and negative fields. This is ascribed to spin configurations frozen during growth.

Quantitative study of the quadratic magneto-optical Kerr effects in Fe films

“…A general numerical treatment of the MOKE, undertaken by solving Maxwell's equations and considering standard boundary conditions, was developed by Yeh [26] and Visnovsky et al [27,28]. For an anisotropic medium, the permittivity tensor ε , which contains information about the refractive index n , MO coupling constant K , 11 G , 12 G , and 44 G , describes the MO properties. The evaluation of the MO quantities starts from a calculation of the eigenmodes in this magneto-optical medium.…”

“…The first theoretical prediction of the QMOKE in a ferromagnetic material was proposed by G. Metzger et al in 1965, but the effect was calculated to be very small [10]. Experimental evidence of the QMOKE was reported by Zhong et al for Ni-Fe bilayers without the knowledge that it was a quadratic effect [11,12]. The QMOKE was experimentally proven to exist in Fe and Co thin films by Osgood et al, who considered the QMOKE to be related only to the magnetization term L T m m ( L m and T m are the longitudinal and transverse magnetization components, respectively) [13].…”

Separation of the first- and second-order contributions in magneto-optic Kerr effect magnetometry of epitaxial FeMn/NiFe bilayers

“…However as first shown by Osgood et al 15 second-order magneto-optic effects can be important in thin films with in-plane anisotropy. In particular for magnetization reversal measurements using MOKE magnetometry the second-order contributions can lead to asymmetric hysteresis loops 15,16,17,18,19 , which are not observed using other magnetometry methods. On the other hand in exchange bias systems, which consist of a ferromagnet exchange coupled to an antiferromagnet, asymmetric hysteresis loops have been reported independently of the magnetometry method 20,21,22,23,24,25,26 .…”

Observation of recoil magnetization curves outside the major loop in Co, Fe, and Ni films

“…The kink in M(H ) predicted by our simulations is clearly present in experimental loops [see Figs. Such a behavior has previously been observed though it has remained unexplained [13,17,18].…”