7–10 Sept 2020
Europe/Zurich timezone
20. konference českých a slovenských fyziků

COMPLEX VOLUME CHANGES INDUCED BY HIGH PRESSURE AND EXTERNAL MAGNETIC FIELD IN NI 2 MNSN-BASED HEUSLER ALLOY

9 Sept 2020, 15:50
30m

Speaker

Kamarád J. (Institute of Physics ASCR, Prague)

Description

The Heusler Ni 2 Mn 1+x Sn 1-x alloys exhibit structural martensitic transformation from cubic
(austenite) into orthorhombic (martensite) phase in a narrow composition range, 0,4 ≤ x ≤ 0,6,
only. The transformation is accompanied by a significant changes of volume, magnetization
and by large anomalies in transport properties. We have studied forced volume magneto-
striction, Joulian magnetostriction, thermal expansion and effect of high pressure on
magnetization of the Ni 1.92 Mn 1.56 Sn 0.52 alloy in wide range of temperature, magnetic field and
pressure. The pronounced decrease of magnetization under pressure, = -11.810 -3 GPa -1 ,
points to an itinerant character of magnetism of the alloy. Using the Maxwell relation, dω/dH
= - ρdM/dP, the received value of dlnM/dP can be perfectly compare with value of forced
volume magnetostriction, dω/dH = 3.11
10 -6 T -1 , received by dilatometric measurement at
field above 0.3 T. The Joulian magnetostriction at low temperature and low magnetic field
(with ΔL || < 0 and ΔL ┴ > 0) confirms a competition between strengths of magnetocrystalline
anisotropy and elastic energy in martensite of Ni 1.92 Mn 1.56 Sn 0.52 that is characterized by a zig-
zag twins structure. The relevant model proposed by O´Handley will be discussed. The
observed change of volume during martensitic transformation of the alloy was verified by X-
ray diffraction measurements.

Presentation materials