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The acoustical investigations of a Ni53Mn25Ga22 Heysler alloy ferromagnet crystal
|Vasiliy D. Buchelnikov 1, V V. Koledov 2, Dmitriy A. Kostiuk 3, Yuri A. Kuzavko 4, Vladimir V. Khovailo 2, Vladimir G. Shavrov 2|
1. Chelyabinsk State University (ChelSU), Br. Kashirinykh Str, 129, Chelyabinsk 454021, Russian Federation
Some metal alloys have reversible thermoelastic martensite transitions with shape memory effects (SME). SME coupled with a reversible transitions from a deformed martensite phaseinto the high-temperature austenitic ones. Ferromagnetic crystal of Ni53Mn25Ga22 Heysler alloy (austenite starting temperature As=1160C and finishing one Af=1340C, martensite starting temperature Ms=1090C and finishing one Mf=970C, Curie temperature Tc=1340C) with a coupled magnetostructural transithions allowes to get the decrease of a magnetic field magnitude, to controll the reversible change of the sample dimensions (4x4x10 mm sample in our case). For our crystal of Ni53Mn25Ga22 the lattice parameters a=b=0.7753 nm, c=0.6598 nm, as for Ni2MnGa a=b=0.5920 nm, c=0.5566 nm at D4hphase, a=0.5825 nm at Oh. The investigations of SME are aimed to combine rapid response with large reversible deformations. The decrease of a magnetic field magnitude for a controlled SME is a common problem for a wide engineering applications of such materials.
The presence of a soft acoustical transverse mode TA2with k=(1/3, 1/3, 0) wave vector and  polarization takes place for Heysler alloys. It is related with accession to zero of the elastic constant c'=(c11-c12)/2 .
The sample was temperature-controlled in experiment. The accuracy of measuring was 0.025 К, the minimal speed of heating - 1 К / 3 min., the sample was placed in constant magnet of 2 kOe at necessity. All five characterizing temperatures of crystal were definable from acoustical measuring.
Authors are grateful for BRFFI and RFFI (F04R-080, 04-02-81058 grants) and ME RB (grant 05-505) for their financial support of carried out researches.
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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium E, by Yuri A. Kuzavko
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-14 23:43 Revised: 2009-06-07 00:44