Thermomagnetic hysteresis effects in NiMn and NiMnPd thin films
dc magnetization measurements, for zero-field cooled (M{sub ZFC}) and field-cooled (M{sub FC}) cases, have been carried out for flash-evaporated Pd-doped NiMn thin films. These included reentrant phases (Ni{sub 76{minus}x}Pd{sub x})Mn{sub 24}, for 0{le}x{le}5, and Ni{sub 75}Mn{sub 23}Pd{sub 2}, a pure spinglass phase. The studies were performed over the temperature range 3{endash}300 K. Low-field magnetization measurements show the irreversibility effect (M{sub ZFC} and M{sub FC} diverge) at temperatures below the Curie temperature T{sub c}. In Ni{sub 75}Mn{sub 23}Pd{sub 2}, M{sub ZFC} falls below M{sub FC}, as usually observed. However, in reentrant compositions, M{sub ZFC} crosses M{sub FC} upon warming into the ferromagnetic regime, where it stays above M{sub FC} at temperatures below T{sub c}. This unusual behavior is attributed to a model of Imry and Ma in which, in a ferromagnet with antiferromagnetic impurities, the impurities can couple to the host ferromagnetic alignment and force the system to break into domains antiferromagnetically coupled to each other. Field-cooled hysteresis measurements indicate the uniaxial anisotropy in these samples to be small, in contrast with the rigid uniaxial anisotropy reported for the corresponding polycrystalline bulk samples. Since the lattice-orbit coupling is weak in the amorphous phase, this clearly demonstrates that the physical origin of the unidirectional anisotropy is associated with the spin-orbit coupling. {copyright} 2001 American Institute of Physics.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40203953
- Journal Information:
- Journal of Applied Physics, Vol. 89, Issue 11; Other Information: DOI: 10.1063/1.1362650; Othernumber: JAPIAU000089000011007044000001; 493111MMM; PBD: 1 Jun 2001; ISSN 0021-8979
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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