Temperature-driven growth of antiferromagnetic domains in thin-film FeRh.

The evolution of the antiferromagnetic phase across the temperature-driven ferromagnetic (FM) to antiferromagnetic (AF) phase transition in epitaxial FeRh thin films was studied by x-ray magnetic linear and circular dichroism (XMLD and XMCD) and photoemission electron microscopy. By comparing XMLD and XMCD images recorded at the same temperature, the AF phase was identified, its structure directly imaged, and its evolution studied across the transition. A quantitative analysis of the correlation length of the images shows differences between the characteristic length scale of the two phases with the AF phase having a finer feature size.

High spatial resolution Raman thermometry analysis of TiO2 microparticles.

A new technique of high-resolution micro-Raman thermometry using anatase TiO2 microparticles (0.5-3 μm) is presented. These very high spatial resolution measurements (280 nm) reveal temperature gradients even within individual microparticles.

Thermodynamic measurements of Fe-Rh alloys.

FeRh undergoes an unusual antiferromagnetic-to-ferromagnetic (AFM-FM) transition just above room temperature (T(AFM>FM)) that can be tuned or even completely suppressed with small changes in composition. The underlying temperature-dependent entropy difference between the competing AFM and FM states that drives this transition is measured by specific heat as a function of temperature from 2 to 380 K on two nearly equiatomic epitaxial Fe-Rh films, one with a ferromagnetic ground state (Fe-rich) and the other with an antiferromagnetic ground state (Rh-rich). The FM state shows an excess heat capacity near 100 K associated with magnetic excitations that are not present in the AFM state.

Fe spin reorientation across the metamagnetic transition in strained FeRh thin films.

A spin reorientation accompanying the temperature-induced antiferromagnetic (AFM) to ferromagnetic (FM) phase transition is reported in strained epitaxial FeRh thin films. (57)Fe conversion electron Mössbauer spectrometry showed that the Fe moments have different orientations in FeRh grown on thick single-crystalline MgO and in FeRh grown on ion-beam-assist-deposited (IBAD) MgO. It was also observed, in both samples, that the Fe moments switch orientations at the AFM to FM phase transition.

Heat transfer simulation and thermal measurements of microfabricated x-ray transparent heater stages.

A microfabricated amorphous silicon nitride membrane-based nanocalorimeter is proposed to be suitable for an x-ray transparent sample platform with low power heating and built-in temperature sensing. In this work, thermal characterization in both air and vacuum are analyzed experimentally and via simulation. Infrared microscopy and thermoreflectance microscopy are used for thermal imaging of the sample area in air.