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Effects on substitution of Ge by In on structural and magnetic properties are studied in MnCoGe 1- x In x compounds. A small amount of In (2% and 5%) dopant can shift the martensite transformation temperature to room temperature and make it overlap with Curie temperature window, which results in a spin-lattice coupling and a large conventional magnetocaloric effect. Giant values of magnetic entropy change ( △S M ) are obtained in both magnetizing and demagnetizing processes in the vicinity of the magnetostructural transition. The maximum values of | △S M | for MnCoGe 0.95 In 0.05 reach 21.4 and 25.4 J/kg K for a small magnetic field change △H  = 2–0 and 0–2 T, respectively, which make it promising for room temperature magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

We report on the growth of single-crystal ErFeMnO 4 and its magnetization, resistivity, and dielectric dispersion behaviors for varying temperature and electric field. A clear bifurcation between the in-plane and out-of-plane M (T) curves is observed due to a paramagnetic-ferrimagnetic transition with a transition temperature of ∼301 K, which is higher than for other R Fe 2 O 4 or substituted compounds. Over a similar temperature range, sudden changes in both the relative permittivity and resistivity were also observed, indicating a strong connection between the magnetization, resistivity and dielectric properties. It can be concluded that the electron transfer between the Fe-site ions plays an important role in these behaviors. Finally, a large relative tunability of 75.9% for relative permittivity ε r and a net polarization P of about ∼408.7 μC/m2 were attained for a DC biased electric field E = 25 kV/m at 390 K, which are promising for the application of tunable ferroelectric devices. [ABSTRACT FROM AUTHOR]

Abstract: We studied the magnetic property, heat capacity, and magnetocaloric effect of TmGa and HoGa single crystals. The observed magnetizations at three principal crystallographic axes display clear magnetic anisotropy, indicating an easy magnetic direction at the a-axis for TmGa and c-axis for HoGa. The measured specific heat of TmGa revealed the Curie temperature of 15K and spin-reorientation temperatures at about 12.5 and 3.0K respectively. Both samples exhibit giant reversible anisotropic magnetocaloric effect based on a second-order phase transition. Along the easy axis, the maximum value of magnetic entropy change for a magnetic field change of 0–5T reaches 26.1Jkg−1 K−1 at 15K and 14.9Jkg−1 K−1 at 65K for TmGa and HoGa, respectively. The corresponding relative cooling powers are achieved to be 468 and 924Jkg−1. These values suggest the possibility of using these materials in magnetic refrigeration applications. [Copyright &y& Elsevier]

In this paper, we investigate the critical behavior and the magnetocaloric effect of the polycrystalline MnCo 1- x Ti x Ge samples with x = 0.02, 0.04, 0.06 and 0.08. For such materials, we show that the maximum entropy change S M depends on applied magnetic field H 2/3 . In order to present a detailed study on the critical behaviors, various techniques such as modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis are used to determine the critical exponent β , γ and δ . The exponents calculated from the critical magnetization isotherm are found to obey the Widom scaling relation remarkably well. Moreover, we also report the accuracy of the three methods using the so-called relative slopes (RS) approach. These critical exponents are found similarly to the theoretical values of the mean-field model, consistent with the existence of long-range ferromagnetic interactions. Suitable magnetocaloric effect and good tunable T C responses are good candidates for magnetic refrigeration materials room temperature. [ABSTRACT FROM AUTHOR]

MnCoGe-based alloys have recently attracted much attention due to their possible large magnetocaloric effect related to the magnetostructural coupling. In this paper, we report a comprehensive study of the spontaneous magnetization and magnetic entropy change of MnCo 1- x Cd x Ge ( x = 0.04 and x = 0.06) alloys for magnetization and demagnetization modes. Landau theory and the dispersion width of the vertical spread of normalized magnetic entropy curves are performed to confirm the second-order transition in this series, consistent with the Banerjee criterion. The maximum isothermal entropy change is presented to depend on magnetic field as follows: |Δ S Max | = A ( H + H 0 ) 2/3 – AH 0 2/3 + BH 4/3 . Here A and B are the intrinsic parameters, and H 0 is a measure of homogeneity. Moreover, we verify the validity and usefulness of magnetic entropy change to estimate the spontaneous magnetization in this system. Finally, these new findings and related discussions with negligible hysteretic losses contribute to the research on the magnetic properties and magnetocaloric potentials in thermomagnetic applications. [ABSTRACT FROM AUTHOR]

• Magnetic property of Heusler alloy Ni 43 Mn 46 Sn 9 Ge 2 with excess Mn was studied in detail. • The visible exchange bias, large coercivity and double-shifted hysteresis behaviors at low temperatures were observed and discussed. • Multiple magnetic phase transitions induced by magneto-structural coupling result in direct and inverse magnetocaloric effects. • Under µ 0 H = 5 T, the maximum value of magnetic entropy change (ΔS M max) reaches 22.88 J/kg.K, the refrigeration capacity (RC) reaches 125.89 J/kg. • ΔS M max increases at a rate of 4.58 J/kg.K per Tesla, while RC increases at a rate of 25.18 J/kg per Tesla. Multiple magnetic and structural phase transitions and magnetocaloric effect of Ni 43 Mn 46 Sn 9 Ge 2 Heusler alloy were detailedly investigated. The martensitic and inverse-martensitic transitions occur at temperatures slightly below room temperature, which induces a ferromagnetic - antiferromagnetic transition and large inverse magnetocaloric effect. A paramagnetic - ferromagnetic and antiferromagnetic - ferromagnetic transition was observed in high-temperature austenitic and low-temperature martensitic phase, respectively. The evident thermomagnetic irreversibility at low temperatures of the martensitic phase suggests a reentrant spin glass state, which originates from the frustration of the competing ferromagnetic and antiferromagnetic spins and results in the visible exchange bias, large coercivity and double-shifted hysteresis behaviors. A T - μ 0 H phase diagram was finally constructed. [ABSTRACT FROM AUTHOR]

• A systematic study was carried out based on the magnetic and specific heat measurements for La 0.7 Ca 0.3 Mn 0.9 Cu 0.1 O 3 synthesized by the solid-state reaction method. • As the temperature decreases from room temperature, the sample undergoes multiple magnetic phase transitions. The corresponding Arrott plots represent the first-order nature of FM transition. • The LCMCO sample exhibits apparent MCE around T C and T SR. Although the Δ S M values are not very big, the wide double peaks distribute and make a large RC. • The -Δ S M values of T SR is larger than that of T C under a relatively weak magnetic field (H ≤ 2 T), so does RC and Δ T ab. • The calculated Δ C P by using Δ S M (T , H) data is in agreement with other experimental magnetic and specific heat results. Perovskite La 0.7 Ca 0.3 Mn 0.9 Cu 0.1 O 3 manganite was prepared and examined by X-ray diffraction. Multiple magnetic phase transitions and magnetocaloric effect were represented based on magnetic and specific heat measurements. The sample undergoes a first-order ferromagnetic - paramagnetic transition with a large thermal hysteresis, where the Arrott plots show negative slopes. A charge ordered phase occurs at T CO = 162 K, which can be melted under a sufficiently large magnetic field (µ 0 H ≥ 1 T) and thus result in a spin reorientation. The step-like jump of magnetization at T b = 42 K in warming curves is caused by a blocked state, which is overcome by applying a magnetic field and leads to a metamagnetic transition. The successive multiple magnetic phase transitions broaden the operating temperature span and contribute to a large refrigerant capacity, in spite of mediocre magnetic entropy change and adiabatic temperature change. The adiabatic temperature change and phase transition mechanism were also discussed based on the recorded specific heat data. [ABSTRACT FROM AUTHOR]