PNR study of the phase transition in FeRh thin films

Abstract

The first order antiferromagnetic to ferromagnetic metamagnetic phase transition of equiatomic FeRh offers new opportunities for novel antiferromagnetic memories and spintronic devices with the caveat that it can be utilized in thin film structures (<50 nm). Here, we report a polarized neutron reflectivity (PNR) study for three representative film thicknesses (5, 20, and 50 nm) aimed at determining the physical and magnetic structure of FeRh at room temperature and partway through the transition. The PNR results are analyzed with reference to X-ray diffraction, X-ray reflectivity, and atomic force microscopy data which together provide a consistent description of the magnetic and physical state of the FeRh thin films. The data demonstrate that the nucleation of the ferromagnetic phase initiates at the MgO substrate, and results from structural and magnetic measurements demonstrate that the magnetic behavior and strain properties of FeRh correlate with the evolving topography of the three films investigated.

Repeatable and deterministic all electrical switching in a mixed phase artificial multiferroic

“…3 . In the zero electric field case, on heating to 175 °C (red circles) the film reaches a maximum magnetisation of 750 emu cm −3 , consistent with previous observations from FeRh films of similar thickness 47 , 48 . The cooling curve (blue circles) reveals a hysteresis of ∼ 25 °C, which is also typical for FeRh of this thickness 49 .…”

“…3 for heating and cooling respectively) shows that the FeRh has a substantial magnetisation of 141 emu cm −3 at room temperature. By contrast, for FeRh on MgO the magnetisation at room temperature is usually very close to zero 47 . This residual FM component may result from poor epitaxy at the PMN-PT interface and/or inadvertent doping with highly mobile Pb atoms 52 .…”

Polarized neutron reflectometry characterization of interfacial magnetism in an FePt/FeRh exchange spring

“…Here we present PNR data on an Fe 55 Pt 45 (10)/ Fe 50 Rh 50 (30)/Pt(1) thin-film sample, where the numbers in parentheses denote nominal thicknesses in nanometers. This study follows from our previous work, in which we characterized the nucleation and progression of the FM phase in FeRh using PNR, and elucidate a critical dependence of the magnetic depth profile on surface morphology [24]. The hybrid anisotropy FePt/FeRh structure studied here provides a pathway to an implementation of heat-assisted magnetic recording (HAMR) in which operational temperatures are reduced by the exchange-spring mechanism [25].…”

“…to epitaxial strain [39], metallic interdiffusion [24], or the coexistence of α' and γ phases of FeRh during the initial growth due to differences in FeRh-MgO and FeRh-FeRh bond energies [40]. Here, the 25 °C mSLD, shown in Fig.…”

Determination of sub-ps lattice dynamics in FeRh thin films

“…The annealing step is important to achieve the necessary B2 crystal structure for the required meta-magnetic state 56 . Further details of the deposition can be found in previously published work 57 , 58 . The sample was prepared for X-ray measurements by cutting it into a 5 × 5 mm square using a diamond saw.…”