Temperature-Induced Metamagnetic Transition and Domain Structures of Single-Crystalline FeRh Thin Films on MgO(100)
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Beschreibung
Exchange systems of FeRh with a hard magnetic layer are a promising approach
for heat-assisted magnetic recording that can largely increase the storage density
of hard disk drives. The FeRh alloy is known to undergo a temperature-induced
metamagnetic transition from antiferromagnetic (AFM) to ferromagnetic (FM) just
above the room temperature. But the AFM and FM phases coexist across the transition
in single-crystalline FeRh thin lms with thin capping layers (e.g. Au, Al,
or MgO). In order to investigate the intrinsic surface magnetic properties, singlecrystalline
FeRh lms without capping layer are prepared by two kinds of experimental
procedures.
For the ex-situ sample preparation procedure, two 40nm thick, single-crystalline
FeRh lms are prepared on MgO(100) by separate layer deposition of Fe and Rh.
X-ray photoemission spectroscopy (XPS) immediately after the deposition shows
that one sample is Rh-rich and the other Fe-rich. The samples are exposed to
air and transferred to a second ultra-high vacuum (UHV) system to perform the
magnetic characterization. This transfer results in a contamination by C and O.
After surface cleaning by high-temperature annealing the Rh-rich sample is still
slightly contaminated with C, while the Fe-rich surface is oxidized. Magneto-optical
Kerr eect (MOKE) measurements reveal that only the Rh-rich sample shows the
metamagnetic transition below room temperature. The Fe-rich sample is FM at
193 and 293 K. Scanning electron microscopy with polarization analysis (SEMPA)
reveals that the Rh-rich surface is FM at all temperatures between 160 and 450K
although the bulk is AFM below room temperature.
For the in-situ sample preparation procedure, a 10nm single-crystalline FeRh lm is
prepared on MgO(100) again by separate layer deposition of Fe and Rh but now in
the same UHV system as all characterizations. Thus, the intrinsic properties of the
single-crystalline FeRh lm are investigated without exposure to air and additional
cleaning steps. The in-situ prepared FeRh lm also exhibits the metamagnetic
phase transition below room temperature as indicated by MOKE. The temperature
dependent domain structure obtained by SEMPA reveals that FM domains exist
at the surface while the bulk is AFM. In contrast to the ex-situ prepared sample
the domain size changes drastically at the transition temperature. This is related
to a spin reorientation transition from out-of-plane to in-plane between 350 to
400 K
Autor*in
Xianzhong Zhou