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

Abstract

Martensitic and magnetic properties of Ni 33:0 Co 13:4 Mn 39:7 Ga 13:9 metamagnetic shape memory alloy were investigated. The kinetic arrest phenomenon was observed at about 120 K by thermomagnetization measurements, and magnetic field-induced transformation (MFIT) was also detected at various temperatures ranging from 4.2 to 300 K. By evaluation of the equilibrium magnetic fields and temperatures based on the transformation fields and temperatures, it was confirmed that the transformation entropy change below 120 K becomes almost zero, which results in the kinetic arrest phenomenon. [doi:10.2320/matertrans.MBW200915] (Received October 14, 2009; Accepted December 28, 2009; Published February 17, 2010) Keywords: NiCoMnGa, metamagnetic shape memory alloy, kinetic arrestRecently, an unusual type of ferromagnetic shape memory (SM) alloy has been found in Ni-Mn-X (X ¼ In, Sn, and Sb) Heusler alloys, 1) where the parent phase shows considerably stronger magnetism than that of the martensite phase.2) Thus a drastic change in magnetization can be obtained during the martensitic transformation. [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. In order to clarify the mechanism of this phenomenon, an alloy with higher Curie temperature is required. We found that in NiCoMnGa alloys, more cobalt can be soluted, the NiCoMnGa alloy system thus having higher Curie temperatures. In this letter, we report the kinetic arrest phenomenon in Ni 33:0 Co 13:4 Mn 39:7 Ga 13:9 polycrystalline alloy. Magnetization measurements at low temperatures were mainly used to investigate the process of martensitic transformation.A polycrystalline Ni 33:0 Co 13:4 Mn 39:7 Ga 13:9 alloy was prepared by induction melting under an argon atmosphere. Heat treatment was then conducted at 1273 K for 24 h in an argon atmosphere for homogenization. The composition of the specimen was determined by wavelength dispersive spectrometry. The magnetization was measured by an extractiontype magnetometer using a superconducting magnet with magnetic field up to 18 T and a superconducting quantum interference device (SQUID) with a magnetic field ranging from 0 to 7 T. Thermomagnetization was measured by SQUID ranging from 6 to 390 K. Moreover, thermal analysis was carried out by differential scanning calorimetry.Figure 1(a) shows the thermomagnetization (MT) curves measured under magnetic fields of H ¼ 0:05, 1, 3 and 5 T, the specimen first being subjected to field cooling (FC) to 6 K, which was followed by field heating back to 390 K, as indicated by the arrows. The inset of Fig. 1(a) shows the different...

The Thermal Transformation Arrest Phenomenon in NiCoMnAl Heusler Alloys

“…By summarizing the results of Ni 45 Co 5 Mn 36.7 In 13.3 [2], Ni 33 Co 13. 4 Mn 39.7 Ga 13.9 [3], Ni 45 Co 5 Mn 31 Al 19 [4] and Ni 37 Co 11 Mn 42.5 Sn 9.5 [5], it can be concluded that the magnetic field hysteresis, which is defined by H hys = H A f − H Ms , greatly increases at low temperatures, which strongly supports the kinetic nature of the KA phenomenon. Moreover, besides the enlargement of the H hys at low temperatures, other experimental facts also support the kinetic nature of this unique phenomenon.…”

“…4 Mn 39.7 Ga 13.9 [3], Ni 45 Co 5 Mn 31 Al 19 [4] and Ni 37 Co 11 Mn 42.5 Sn 9.5 [5]. For these Metamagnetic Shape Memory Alloys (MMSMAs), the ferromagnetic parent phase can be induced by applying a magnetic field from the martensite phase, as first reported in NiCoMnIn [6].…”

“…Physically, if the magnetization differences between the two phases (∆M ) at H Ms and H A f are almost equal, H 0 = (H A f +H Ms )/2 can be assumed as the equilibrium magnetic field at which the parent phase and the martensite phase have an equal Gibbs free energy under the condition that a small amount of the martensite phase exists in the parent austenite matrix [13]. It can be concluded from [2][3][4][5] that H 0 increases with decreasing temperature and becomes almost constant below certain temperatures (KA temperatures), which is a common feature of all four alloys. The Clausius-Clapeyron equation between the magnetic field and temperature gives:…”

Properties and Decomposition of Heusler Alloys

“…[ some years before for Ni-Co-Mn-In alloys (see Figure 6). [32][33][34][35][36][37] As in Figure 5, Figure 6shows results of rapidly quenched samples.…”

Effect of interfacial pinning on the thermo-remanent magnetization of disorder Mn50Ni38.5Sn11.5 alloy

“…Despite these complexities, a considerable effort has been made to understand the first order phase transformation (FOPT) in the magnetic field (H)-temperature (T) phase space since the FOPT is influenced by both H and T [3,[8][9][10]. It is already proved that a kinetically arrested magnetic FOPT gives rise to a magnetically ordered martensite state in the low temperature [11][12][13]. In this investigation we have studied the thermo-remanent magnetization (TRM) behaviour of low temperature martensite phase while cooling the system under high H through the selected temperature regime.…”