High Field Magnetization in Manganese Intermetallic Compounds(Magnetism)

Magnetization measurements were carried out on manganese intermetallic compounds Mn_3MC(M=Ga, Zn), Mn_Co_xSb(x=0.09 and 0.15) and MnMX(M=Ru, Rh, Pd;X=As, P)in magnetic fields up to 150 or 320 kOe. Antiferromagnetic(AF)-ferromagnetic(F) field-induced transitions and (AF+F)-(F) one were observed for Mn_3GaC and Mn_3ZnC, respectively. For Mn_Co_Sb, intermediate(I)- ferrimagnetic(Fr) field-induced transitions were observed. For Mn_Co_Sb, AF-Fr field-induced transitions were observed. These transitions were of the first order except one of Mn_3ZnC. The magnetic properties of MnMX (M=Ru, Rh, Pd;X=As, P) were discussed on the basis of the values of magnetization and high-field magnetic susceptibility

Magnetic Field-Induced Strain of Metamagnetic Heusler Alloy Ni41Co9Mn31.5Ga18.5

Ni41Co9Mn31.5Ga18.5 is a re-entrant and metamagnetic Heusler alloy. In order to investigate the magnetic functionality of polycrystalline Ni41Co9Mn31.5Ga18.5, magnetic field-induced strain (MFIS) measurements were performed. A 0.12% MFIS was observed at 340 K and 10 T. Strict MFISs between 330 and 370 K were observed. These magneto-structural variances acted in concert with the metamagnetic property observed by the magnetization measurements and magneto-caloric property observed by the caloric measurements in applied magnetic fields. The MFISs were proportional to the fourth power of the magnetization, and this result is in agreement with Takahashi’s spin fluctuation theory of itinerant electron magnetism. The investigation of time response of the MFIS was performed by means of water-cooled electric magnet, zero magnetic field to 1.66 T in 8.0 s at 354 K. A 2.2×10−4 MFIS was observed, which was 80% of the MFIS in a 60-s mode. This indicates that a high-speed transition has occurred on applying magnetic fields

Magnetocaloric Effects in Metamagnetic Shape Memory Alloys

Recently, metamagnetic shape memory alloys have attracted much attention as candidates for the rare-earth free magnetic refrigerants. These materials undergo the martensitic transformation (MT) at around room temperature accompanied by a significant entropy change. The application of the magnetic field at the low-temperature martensitic phase realizes the magnetic field-induced martensitic transformation (MFIMT). Through the MFIMT, the materials show an unconventional magnetocaloric effect (MCE), which is called inverse magnetocaloric effect (IMCE). In this chapter, the direct measurement system of MCE in pulsed-high-magnetic fields is introduced. With taking the advantage of the fast field-sweep rate of pulsed field, adiabatic measurements of MCE are carried out at various temperatures. Using this technique, the IMCEs of the metamagnetic shape memory alloys NiCoMnIn and NiCoMnGa are directly measured as adiabatic temperature changes in pulsed fields. From the experimental data of MCE for NiCoMnIn, the entropy of spin system in the austenite phase is estimated through a simple mean-field model. By the combination of MCE, magnetization and specific heat measurements, the electronic, lattice and magnetic contributions to the IMCE are individually evaluated. The result for NiCoMnIn demonstrates that lattice entropy plays the dominant role for IMCE in this material

Magnetocaloric and Magnetic Properties of Meta‐Magnetic Heusler Alloy Ni41Co9Mn31.5Ga18.5

Ni41Co9Mn31.5Ga18.5 is a magnetic Heusler alloy, which indicates metamagnetic transition at the reverse martensite transition. In this paper, caloric measurements were performed and discussed about magnetocaloric effect. We also performed magnetization measurements around Curie temperature TC in the martensite phase and analyzed by means of the spin fluctuation theory of itinerant electron magnetism. From the differential scanning calorimetry (DSC) measurements in zero fields, the value of the latent heat λ was obtained as 2.63 kJ/kg, and in magnetic fields the value was not changed. The entropy change ΔS was − 7.0 J/(kgK) in zero fields and gradually increases with increasing magnetic fields. The relative cooling power (RCP) was 104 J/kg at 2.0 T, which was comparable with In doped Ni41Co9Mn32Ga16In2 alloy

Heat Capacity of Pd-Si, Ni-Si-B and Zr-Based Metallic Glasses

The specific heat of metallic glasses containing Si and B (Ni_Si_B_ and Pd_Si_) and Zr-based metallic glasses(Zr_Al_Cu_Ni_Co_, Zr_Al_Cu_ and Zr_Cu_) was measured in the temperature range 77-800 K using an a.c. calorimeter. Several exothermic and endothermic processes were observed correspondingly to the transformation sequences for complete crystallization of all the glasses. The structural relaxation process appears with a decrease in heat capacity. For Ni-Si-B and Pd-Si glasses an abrupt increase in the specific heat is observed at the glass transition temperature T_g. For Zr-based glasses, however, a monotonous increase in the specific heat is observed just below T_g. Then the specific heat makes a peak and decrease abruptly with increasing temperature. The height of the peak increases with heating rate