Magnetostructural phase transitions in Ni₅₀Mn_25+xSb_25−xHeusler alloys

Abstract

The structural and magnetic properties of Ni(50)Mn(25+x)Sb(25-x) (0≤x≤18) Heusler alloys have been investigated by x-ray diffraction, magnetization, thermal expansion, and electrical resistivity measurements. Austenitic phases with the L2(1) cubic crystal cell and martensitic phases with Pmm2 orthorhombic structures have been observed at room temperature in alloys with 0≤x≤12.5 and 13≤x≤14, respectively. The Curie temperatures of the austenitic phases decrease linearly with increasing x and change from 370 (x = 0) to 340 K (x = 12.5). In the concentration 7<x≤10, the system is found to undergo martensitic phase transitions above 150 K. The martensitic transition temperatures increase rapidly with increasing x and for x≥13.5 the temperature exceeds the Curie temperature of the austenitic phase (340 K). The alloys in their martensitic phases exhibit complex magnetic behavior. The phase diagram with respect to temperature and composition of the Ni(50)Mn(25+x)Sb(25-x) system has been determined, where the following magnetic phases have been observed in the martensitic state: antiferromagnetic phase (14<x); paramagnetic and antiferromagnetic (13≤x≤14, above 120 K) mixed phase; ferromagnetic and antiferromagnetic (10≤x≤14, above 20 K) mixed phase. The mixed phases result in observation of the exchange bias effect at low temperatures (below 120 K).

Kinetic Arrest of Martensitic Transformation in Ni<SUB>33.0</SUB>Co<SUB>13.4</SUB>Mn<SUB>39.7</SUB>Ga<SUB>13.9</SUB> Metamagnetic Shape Memory Alloy

“…[3][4][5] In these alloys, an application of magnetic field strongly decreases the martensitic transformation temperatures and a magnetic field-induced transformation, namely, metamagnetic phase transformation, has also been confirmed in NiCoMnIn, 6) NiCoMnSn 13,14) alloys, the kinetic arrest phenomenon has been reported. In this phenomenon, martensitic transformation is interrupted at certain temperatures (noted as kinetic arrest temperature, T KA ) during field cooling and does not proceed with further cooling.…”

“…[3][4][5] In these alloys, an application of magnetic field strongly decreases the martensitic transformation temperatures and a magnetic field-induced transformation, namely, metamagnetic phase transformation, has also been confirmed in NiCoMnIn, 6) NiCoMnSn 7) NiCoMnGa 8) and NiCoMnAl 9) alloys. Moreover, an almost perfect magnetic field-induced SM effect, that is, a metamagnetic SM effect, has been found in single crystalline 16 13,14) alloys, the kinetic arrest phenomenon has been reported.…”

Pressure induced magnetic and magnetocaloric properties in NiCoMnSb Heusler alloy

“…Recently, we have reported a large enhancement of MCE with Co substitution in NiMnSb. 18 In this paper, we report the effect of pressure on the magnetic and MC properties of Ni 50−x Co x Mn 38 Sb 12 . It was found that the substitution of Co for Ni reduces the martensitic transition temperature.…”

Thermodynamics and Kinetics of Martensitic Transformation in Ni-Mn-based Magnetic Shape Memory Alloys

“…Substitutional Ni-Mn-based alloy systems such as Ni-Co-Mn-Sn [15], Ni-Co-Mn-Ga [16] and Ni-Co-Mn-Al [17], ferrous systems such as Fe-Mn-Al [18], Fe-Mn-Ga [19] and Fe-Mn-Al-Ni [20], as well as cobalt based Co-Cr-Ga-Si alloys [21] have been reported. In these alloys, there is a strong output stress during the a Corresponding author's e-mail: kainuma@material.tohoku.ac.jp MFIT [22][23][24] though a strong magnetic field is needed for the realization of MMSMA.…”