Ferromagnetic Ni-Mn-Ga films were fabricated by depositing on MgO (001) substrates at temperatures from 673 K to 923 K. Microstructure, crystal structure, martensitic transformation behavior, and magnetic properties of the films were studied. With increasing deposition temperature, the surface morphology of the films transforms from granular to continuous. The martensitic transformation temperature is not dependent on deposition temperature; while transformation behavior is affected substantially by deposition temperature. X-ray analysis reveals that the film deposited at 873 K has a 7M martensite phase, and its magnetization curve provides a typical step-increase, indicating the occurrence of magnetically induced reorientation (MIR). In situ magnetic domain structure observation on the film deposited at 873 K reflects that the martensitic transformation could be divided into two periods: nucleation and growth, in the form of stripe domains. The MIR occurs at the temperature at which martensitic transformation starts, and the switching field increases with the decrease of temperature due to damped thermal activation. The magnetically induced martensitic transformation is related to the difference of magnetization between martensite and austenite. A shift of martensite temperature of dT /dH = 0.43 K/T is observed, consistent with the theoretical value, 0.41 K/T.

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Relation between martensitic transformation temperature range and lattice distortion ratio of NiMnGaCoCu Heusler alloys *Wei Jun(韦 俊) a)b) , Xie Ren(谢 忍) a) , Chen Le-Yi(陈乐易) a) , Tang Yan-Mei(唐研梅) a) , Xu Lian-Qiang(许连强) a) , Tang Shao-Long(唐少龙) a) † , and Du You-Wei(都有为) a) a)

Pr(Fe1-xCox)2 ribbons have been prepared by melt-spinning method. Their structure, magnetic properties and thermal stability are investigated. It is found that Pr(Fe,Co)2 cubic Laves phase can form only when x≥0.2 at wheel speed of 45m/s. For Pr(Fe0.6Co0.4)2 alloy, at wheel speed of 30m/s, the ribbon consistes of a mixture of Pr2(Fe,Co)17, Pr(Fe,Co)2 and rare earth-rich phase. Almost Pr(Fe0.6Co0.4)2 compound a small amount of amorphous phase is observed at wheel speed up to 45m/s. Pr(Fe0.6Co0.4)2 compound becomes unstable above 770℃. The resub-bonded Pr(Fe0.6Co0.4)2 nanocrystalline compound which is obtained at wheel speed of 40m/s combines high magnetostriction (λ∥-λ⊥=140×10-6), with significant magnetic coercivity, iHc=398kA/m.