| AVS 54th International Symposium | |
| Magnetic Interfaces and Nanostructures | Wednesday Sessions |
| Session MI-WeM |
| Session: | Magnetic Thin Films and Nanostructures |
| Presenter: | D.A. Arena, Brookhaven National Laboratory |
| Authors: | Y. Ding, Brookhaven National Laboratory D.A. Arena, Brookhaven National Laboratory L.H. Lewis, Northeastern University J. Dvorak, Montana State University C. Kinane, University of Leeds, UK M. Ali, University of Leeds, UK C.H. Marrows, University of Leeds, UK B.J. Hickey, University of Leeds, UK |
| Correspondent: | Click to Email |
Thin films of FeRh alloys with near equiatomic composition and CsCl type ordering exhibit an intriguing antiferromagnetic (AFM) to ferromagnetic (FM) first-order phase transition near 100° C. This easily accessible phase transition has generated interest in using FeRh films as a temperature-tunable AFM pinning layer in exchange-biased magnetic structures.1 The AFM to FM transition is associated with the dramatic increase of the saturation magnetization Ms, along with temperature hysteresis of Ms, and a variation in the lattice parameter. We have grown high quality, epitaxial FeRh films on MgO(100) via molecular beam epitaxy (MBE); film thickness ranged from ~200 Å to 1000 Å. The films are characterized with a combination of laboratory-based magnetometry and synchrotron-based x-ray diffraction (XRD) and x-ray magnetic circular dichroism (XMCD). Magneto-optic Kerr effect measurements and SQUID magnetometry confirm the AFM to FM transition in the films. Temperature dependent XRD indicates an expansion of the out-of-plane lattice parameter across the phase transition which mirrors the change in Ms. XMCD spectra were collected in conventional total electron yield (TEY) mode, which probes the near-surface region (probe depth ~50 Å - 100 Å) and in indirect transmission mode (ind-trans), where the oxygen K-edge fluorescence from the MgO substrate is monitored as the photon energy is swept through the Fe L2,3 core levels. For the Au capped films, TEY scans reveal a FM near-surface region even at room temperature, while the ind-trans mode data are consistent with a bulk AFM state at ambient temperatures which transforms to a FM state above 100° C. The choice of capping layer also affects the room-temperature magnetism in the near-surface region as the MgO capped films do not exhibit an appreciable XMCD signal in TEY mode.
1Thiele. et al., Appl. Phys. Lett.,82, 2859 (2003).