Strong uniaxial anisotropies of iron grown on UHV cleaved InAs(110) investigated by correlated scanning tunneling microscopy and ferromagnetic resonance

Abstract

The magnetic properties of iron films grown under UHV condition are governed by the deposition condition and the substrate preparation. One way of producing almost perfect surface conditions with large terrace width and exact orientation is cleaving. With this method no additional cleaning process of the surface is needed. Here we present our investigations of iron films (thickness: 0.1–30nm) grown on UHV cleaved InAs substrates using in situ scanning tunnel microscopy (STM) investigations combined with in situ magneto-optical Kerr effect (MOKE) and ex situ angle and frequency dependent conventional ferromagnetic resonance (FMR). The (110) InAs surface allows the investigation of three magnetic axes: in-plane easy (001), hard (111), and intermediate (110) axes of the iron layer. The (110) symmetry of the magnetic cubic crystalline anisotropy should lead to angles of 110° and 70° between the hard axes, respectively. STM images of the clean InAs(110) show 500nm wide terraces with mono atomic steps predominately oriented parallel to the (001) direction. MOKE hysteresis loops were measured during the Fe deposition to prove the ferromagnetic state. The angle dependent in-plane FMR measurement revealed unexpected 90° symmetry. Deducing the anisotropy constants from the FMR resonance position, one finds a slightly increased bulk crystalline anisotropy and a uniaxial anisotropy of the same order of magnitude. This strong uniaxial anisotropy distorts the 110° symmetry to 90° symmetry. The correlation of frequency and angle dependent FMR and STM measurements evidences that the uniaxial anisotropy is due to the dislocations caused by the orientation of the terraces.