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The effects of Ti substitution for Mn and heat treatment on structural, magnetic, and magnetocaloric properties of CoMnGe alloy have been investigated using electron microscopy, X-ray diffraction, calorimetric, and magnetic measurements. According to X-ray diffraction measurements, CoMnTiGe alloys are in a single phase hexagonal structure at room temperature. It is found that the as-cast CoMnTiGe alloy shows a magnetostructural phase transition close to room temperature. The transition shows a large magnetic entropy change and a small hysteresis in the isothermal magnetic field-dependent magnetization measurements. After annealing, the phase transition temperature decreases slightly and the magnetization is sharply decreasing at Curie temperature. The sharp change of magnetization at phase transition temperature is accompanied by a significant increase in the magnetic entropy change, i.e., magnetic entropy change value for the magnetic field change of 1 T was increased from −3.3 to −6.3 J kg K. Moreover, after annealing, hysteresis losses reduced significantly for ∆ H = 7 T. Accordingly, the heat treatment has a significant effect on magnetocaloric properties of the CoMnTiGe alloy. [ABSTRACT FROM AUTHOR]

A nanostructured NdMn2Ge2 sample is prepared by a high-energy ball-milling technique. The structural and magnetic properties of ball-milled nanopowder have been studied by high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), magnetic force microscopy (MFM), and magnetization measurements. According to the HRTEM results, the particle size of the nanoparticles changes from 5 to 11 nm. Curie and spin-reorientation temperatures are found to be 328 and 208 K from the temperature-dependent magnetization measurements, respectively. The maximum magnetic entropy change values are about −0.4 and −1.10 J kg−1 K−1 for Δ H = 2 T around the spin-reorientation ( TSR) and Curie ( TC) temperatures, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The thermal and magnetothermal properties of La0.5Pr0.5Mn2Si2 and isostructural LaFe2Si2 intermetallic compounds in the temperature range 4.5–303 K are reported with and without applied magnetic field. The electronic, lattice, and magnetic contributions to the heat capacity of La0.5Pr0.5Mn2Si2 are determined and analyzed. We have determined and from heat capacity experiments; the values are in line with those from the magnetization measurements. We conclude that in order to observe the anomaly in the heat capacity data around in the system, the transition around should occur in a narrow temperature interval. [Copyright &y& Elsevier]

Abstract: The La1− x Ce x Mn2Si2 compounds (x=0.35 and 0.45) exhibit an antiferromagnetic–ferromagnetic transition caused by the changes in distance between Mn atoms due to temperature changes. A field-induced transition from antiferromagnetic state to ferromagnetic state at a critical field, which decreases with increase in temperature, can also be induced by applying a magnetic field. In this paper our aim is to study the magnetization and magnetocaloric effect, close to transition temperatures. Our subsidiary aim is to examine the temperature dependence of critical field and ferromagnetic fraction of compounds. The variation of magnetocaloric effect with temperature is correlated with the ferromagnetic–antiferromagnetic phase coexistence. Our final aim is to examine the harmony between magnetocaloric effect values calculated both by the Maxwell theory and by the Landau theory. [Copyright &y& Elsevier]

Abstract: Nanocrystalline LaMn2Si2 powders have been obtained by high-energy ball milling for 30min from bulk alloys. After milling a high coercivity about 6kOe is observed at 10K in contrast to neglectable coercivity for the bulk LaMn2Si2 at 5K. The average grain size of the optimum particles which is obtained from X-ray diffraction pattern and HRTEM picture is about 20nm. The magnetic hardening is observed for the nanocrystalline LaMn2Si2, reflected in the coercivity field strength of 6kOe at 10K. [Copyright &y& Elsevier]