PROPERTIES OF SPUTTER-DEPOSITED Ni-Mn-Ga THIN FILMS

Mykola M. Krupa 1Volodymyr A. Chernenko 1Manfred Kohl 3Igor V. Lezhnenko 1Makoto Ohtsuka 2Yurii B. Skyrta 1

1. Institute of Magnetism, N.A.S. of Ukraine, 36-b Vernadsky Blvd, Kyiv 252142, Ukraine
2. Tohoku University, Sendai, Japan
3. Forschungszentrum Karlsruhe, IMT, Postfach 3640, Karlsruhe 76021, Germany

Abstract

The ferromagnetic thermoelastic martensites being sputter-deposited as thin films represent novel materials which can be incorporated in the ferromagnetic MEMS, microsensors etc.

Properties of such films are governed by many factors, among them sputter conditions, target composition and heat treatment are worth noting.

Here we study an influence of substrate and heat treatment on the film structure, formation of martensitic phase and ferromagnetic ordering of the submicron thin films sputter-deposited on alumina ceramic and glass substrates using targets of Ni49.5Mn28Ga22.5 and Ni52Mn24Ga24 (at.%).

R.f. magnetron deposition has been used to produce as-deposited Ni-Mn-Ga thin films with thickness ranging from 0.1 to 5 micron. The substrate temperature was kept about 320 K. Annealing of thin films was made in vacuum at 873K for 24h.(glass) and at 1273K for 1h. (alumina).

The structural characterization of films was made by X-ray diffraction and optical microscopy. The temperature dependencies of the electrical resistivity of films were measured in the interval of 290-430 K. On warming, as-deposited on glass films show a small reversible monotonous decrease of resistivity with the kink-like change in the vicinity of 340 K whose nature is not clear yet.The annealed films demonstrate a considerable increase of resistivity and anomalies associated with the martensitic transformation and Curie temperature typical for bulk Heusler alloys. The thermomagnetic curves measured by SQUID in the interval 250-400 K confirm a disordered magnetic state for as-deposited films and saturation magnetization values for annealed films typical for bulk alloy. The optical reflection spectra also show a difference for as-deposited and annealed films.

 

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium C, by Mykola M. Krupa
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-19 12:09
Revised:   2009-06-07 00:44