Correlation of microstructural and magnetic properties of FeRh films presenting first order antiferromagnetic-to-ferromagnetic transition

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

Bariloche

Simposio; XXIII Latin American Symposium on Solid State Physics; 2018

Bulk FeRh is an unusual alloy as it undergoes an infrequent transition from an antiferromagnetic (AF) to a ferromagnetic (F) state upon heating from room temperature (RT) to above TAF􀀀F 330-370 K without developing structural changes. It is a rst order transition that exhibits thermal hysteresis of about 10 K. FeRh is not the only compound that shows this behaviour but it is unique in that TAF􀀀F is signicantly above RT. This fact makes of FeRh a very interesting material for technological applications (such as thermally assisted magnetic recording), especially in the form of thin films. Here we report X-ray diraction (XRD), ferromagnetic resonance (FMR), and dc magnetization results obtained on a set of 100 nm-FeRh lms deposited on MgO (100), MgO (111)and Al2O3(0001) substrates. After deposit, most of our samples were annealed at 700 C in order to induce the chemical order of Fe and Rh atoms, the elimination of residual (paramagnetic) phase, and the promotion of the AF-F transition. XRD data indicate that the lms deposited on MgO (100), Mgo (111) and Al2O3(0001) develop strong [001], [011] and [111] textures, respectively. The magnetic characterization consists on dc magnetization curves and ferromagneticresonance (FMR) experiments. FMR is a powerful technique that is particularly sensible to specic properties of the lms such as shape, magnetocrystalline, and tension-induced anisotropies, becoming a unique tool to trace structural and magnetic transitions. A joint analysis of the measured microstructural and magnetic properties suggests that by using dierent substrates the in-plane strain can be changed from compressive (MgO(100)) to tensile (c-Al2O3), which is a relevant piece of information for direct applications of FeRh lms. Moreover, we found that the observed characteristics of strain nicely reflect on the magnetic properties of the lms, and more especically on the magnetoelastic anisotropy determined by FMR measurements.