Influence of replacement of Mn by Cr on magnetocaloric properties of quenched NiMn1–xCrxGe alloys
E. Zubov1,2, N. Nedelko3, A. Sivachenko4, K. Dyakonov5, Yu. Tyvanchuk6, M. Marzec6, V. Valkov4, W. Bażela8, A. Ślawska-Waniewska3, V. Dyakonov3
A. Szytuła7, and H. Szymczak3
1G.V. Kurdyumov Institute for Metal Physics, NASU, 36 Acad. Vernadsky Boulevard, Kyiv 03680, Ukraine
2Vasyl’ Stus Donetsk National University, Vinnytsia 21021, Ukraine
4О.О. Galkin Donetsk Institute of Physics and Engineering, 46 Nauki Ave., Kyiv 03680, Ukraine
5Ioffe Physico-Technical Institute RAS, St.-Petersburg 194021, Russia
7Institute of Physics, Jagiellonian University, 4 Reymonta, Kraków 30-059, Poland
8Institute of Physics, Krakow University of Technology, 1 Podchorążych, Kraków 30-084, Poland
Received April 13, 2018
In this paper, the crystallographic, magnetic, thermomagnetic, and magnetocaloric properties of the quenched NiMn1–xCrxGe (x = 0.04, 0.18 and 0.25) half-Heusler alloys have been studied by x-ray diffraction, differential scanning calorimetry and magnetization measurements. An influence of partial substitution of Cr for Mn and quenching of the samples on the character of structural and magnetic phase transitions is presented. Quenching of the alloys results in the formation of two phase (orthorhombic and hexagonal) crystal structure. The magnetic properties were investigated by means of magnetization measurements over a wide temperature (5–400 K) and magnetic field (up to 60 kOe) ranges. The experimental data indicate that at quenching and with increasing Cr content the magnetic order changes from antiferromagnetic to ferromagnetic. Hardened compounds exhibit a thermal hysteresis in the vicinity of the magnetic phase transition, what is characteristic for a first-order magnetic phase transition. The magnetic phase transition temperatures are decreased as a result of quenching of the samples. The magnetic entropy changes were calculated using the field dependences of isothermal magnetization in terms of the thermodynamic Maxwell relation. The magnetic entropy changes, |ΔSMmax|, obtained for the hardened alloys with x = 0.25 have the maximum value equal to 23 J/(kg·K) near the magnetic phase transition for a field change of ΔH = 0–60 kOe.
PACS: 75.30.Sg Magnetocaloric effect, magnetic cooling;
Key words: intermetallic alloys NiMn1–xCrxGe, magnetization, magnetic phase transition, magnetic entropy, magnetocaloric effect.
Published online: June 27, 2018