Epitaxiality effects on the magnetic order of single crystalline FeRh thin films

IVAR MAURICIO MONTELLANO; GABRIELA ALEJANDRO; NADIA ÁLVAREZ; A. BUTERA; HARDEEP KUMAR; DANIEL R. CORNEJO

Bariloche

Congreso; Advanced Topics in Magnetism and Superconductivity 2014; 2014

It is well known that bulk bcc FeRh alloys undergo a very unusual transition from an antiferromagnetic (AFM) to a ferromagnetic (FM) state upon heating from room temperature (RT) to above $T_{AF-F} \approx$ 370 K. This is a first order transition that exhibits a thermal hysteresis of about 10 K between heating and cooling. Though FeRh is not the only compound that develops this behavior, it is unique in that the $T_{AF-F}$ is significantly above RT. Beyond the basic interest in the underlying physics, this feature makes of FeRh a very interesting material for technological applications such as thermally assisted magnetic recording. Although the bulk binary system (Fe, Rh) has been extensively studied since the 1940´s and very complete phase diagrams were obtained, very little work is reported on FeRh thin films. In this work we report experimental results obtained on a set of 100 nm FeRh films deposited on MgO (100) and MgO (111) substrates. The x-ray diffraction data indicate that the films grow epitaxially. The magnetic characterization was achieved by performing magnetization curves and ferromagnetic resonance (FMR) experiments. FMR is a powerful technique to investigate the magnetic properties of thin films as it provides a measure of the collective response of the spin system in the FM state. It is particularly sensible to specific properties of the films such as shape, magnetocrystalline, and tension-induced anisotropies, becoming a unique tool to trace structural and magnetic transitions. By varying the temperature from RT to above 450 K we compare the properties of the AFM-FM transition among FeRh films of same thickness but exposed to different post-growth annealings, and deposited on MgO substrates of different crystalline orientation.