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Heusler alloy Mn 50 Ni 40 In 10 was produced as preferentially textured ribbon flakes by melt spinning, finding the existence of martensitic-austenic transformation with both phases exhibiting ferromagnetic ordering. A microcrystalline three-layered microstructure of ordered columnar grains grown perpendicularly to ribbon plane was formed between two thin layers of smaller grains. The characteristic temperatures of the martensitic transformation were M S = 213 K, M f = 173 K, A S = 222 K, and A f = 243 K. Austenite phase shows a cubic L2 1 structure ͑a = 0.6013͑3͒ nm at 298 K and a Curie point of 311 K͒, transforming into a modulated fourteen-layer modulation monoclinic martensite. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2827179͔Since Sutou et al.1 reported the occurrence of martensitic transformation in the ferromagnetic Heusler system Ni 50 Mn 50−x In x , considerable attention has been dedicated to study magnetism and magnetic shape memory effect, [2][3][4] magnetic entropy change, [4][5][6][7][8] and magnetotransport properties 9-11 of these alloys. Nevertheless, ferromagnetism in both phases is only observed in the narrow composition range of 15ഛ x ഛ 16 2 . The characteristic temperatures of the reversible first order structural transformation between both phases, referred as martensitic and austenitic starting and finish temperatures ͑i.e., M S , M f , A S , and A f , respectively͒, strongly vary upon small changes in the chemical composition. The crystal structure of austenite and martensite depends on the composition, 2,4 and the transformation can be also induced by applying a magnetic field.2-4 Additionally, a large inverse and direct magnetocaloric effect has been measured in Ni 50 Mn 34 In 16 .6-8 Ni-Mn-In Heusler alloys are therefore of significant prospective importance for applications in both magnetically driven actuators due to magnetic shape memory effect and as working substances in magnetic refrigeration technology.Until now, the investigated alloys are usually bulk polycrystals obtained by arc or induction melting followed by a high temperature annealing, [1][2][3][4][5][6][7][8]10 or single crystals grown by Czochralski method.9,11 Present investigation was carried out to employ rapid quenching by melt spinning to produce MnNi-In Heusler alloys. This technique offers two potential advantages for the fabrication of these magnetic shape memory alloys: the avoiding, or reduction, of the annealing to reach a homogeneous single phase alloy, and the synthesis of highly textured polycrystalline ribbons. Ribbon shape can be also appropriate for use in practical devices. We fabricated the alloy Mn 50 Ni 40 In 10 by melt spinning. Its valence electronic concentration per atom e / a is 7.801, allowing the existence of martensite-austenite transformation with both phases exhibiting ferromagnetic ordering, opening its potential use as a magnetic shape memory alloy. 3 We report in this letter a preliminary characterization of the microstructural features and magnetic behavior.As-cast pel...

The evolution of the giant magnetoi m p e d a n c e e f f e c t ( G M I ) i n t h e F e 7 3 . 5 S i 1 3 : 5 B g C u l N b~ amorphous alloy wire as a function of the structural and magnetic changes induced by suitable thermal treatments are reported here. The results show that the maximum GMI relative changes and magnetic field sensitivity are observed after annealing in the range of t e m p e r a t u r e s T a = 550-600° C , w h e r e nanocrystallization occurs.This maximum effect is related to the optimum compromise between soft magnetic behaviour and electrical properties, i.e. maximum circular susceptibility and minimum r e s i s t i v i t y .

The recently discovered giant magnetc-impedance (GMI) effect has been measured as a function of circular +ving-field frequency and applied tensile stress on two nearrem-magnetostriction amorphous wires. The effect of different orientations of the induced magneroelastic anisompy has been verified. for the fim time, by using wires with opposite magnetosttiction constant, .Ls, signs ~~,vCo,,.tNh,,sSi,.sBls. i s = 1.5 x IO"; and Co68.IFe4.~Si1*,sBIS1 i s = -4 x IO-'). cMI ratios up to 300% were found in the magnetically softer (lower-magnetostriction) wire. The frequency dependence of GMI bas been found to be strongly influenced by the magnetoelastic anisotropy induced in the amorphous wires. Results are interpreted in terms of changes in the magnetic penatation depth by modifiCations in the circumferential permeability originated by the action of extemal agents as field and mechanical stresses. GMI is therefore found to be largely determined by the magnetic domain configuration and relative contributions of both domain wall motions and magnetic moment rotations to the overall magnetization process.