T. V. Manh

Y-doped La0.7Ca0.3MnO3 manganites exhibiting a large magnetocaloric effect and the crossover of first-order and second-order phase transitions

We prepared orthorhombic La0.7−xYxCa0.3MnO3 samples (x = 0, 0.04, 0.06, and 0.08) by conventional solid-state reaction and then studied their magnetic properties and magnetocaloric (MC) effect based on magnetization versus temperature and magnetic-field measurements, M(T, H). The experimental results revealed that an x increase in La0.7−xYxCa0.3MnO3 reduced the ferromagnetic-paramagnetic transition temperature (TC) from 260 K (for x = 0) to ∼126 K (for x = 0.08). Around the TC, maximum magnetic-entropy changes for a magnetic-field variation interval H = 50 kOe are about 10.7, 8.5, 7.4, and 5.8 J·kg−1·K−1 for x = 0, 0.04, 0.06, and 0.08, respectively, corresponding to refrigerant capacities RC = 250–280 J·kg−1. These values are comparable to those of some conventional MC materials, revealing the applicability of La0.7−xYxCa0.3MnO3 in magnetic refrigeration. Using the Arrott method and scaling hypothesis as analyzing high-field M(H, T) data, and the universal-curve construction of the magnetic entropy chang...

Coexistence of short- and long-range ferromagnetic order in La0.7Sr0.3Mn1−xCoxO3 compounds

Polycrystalline La0.7Sr0.3Mn1−xCoxO3 (x = 0.0–1.0) samples were synthesized by solid-state reaction. Structural and magnetization studies reveal the replacement of Co for Mn in La0.7Sr0.3Mn1−xCoxO3, and the decrease of the Curie temperature (TC) from 360 K (for x = 0) to 224 K (for x = 1). Positive slopes observed in the H/M versus M2 curves prove all the samples undergo a second-order magnetic phase transition. By analysis of the M(H) data at temperatures around TC using the Kouvel-Fisher method, we obtained the values of critical parameters (TC, β, γ, and δ). The results suggest an existence of short-range FM order in the sample x = 0 with β = 0.377. Meanwhile, for the case of Co-doped samples, their β values in the range of 0.403–0.457 indicate a coexistence of short and long-range FM order. This means that Co-doping favors establishing FM long-range order in La0.7Sr0.3Mn1−xCoxO3. From M(H) data, we have also determined the magnetic entropy change (ΔSm) for the samples. We have found that the ΔSm(T) cu...

Magnetic and Magnetocaloric Properties of La 0.8– x Ag x Ca 0.2 MnO 3 Exhibiting the Crossover of First- and Second-Order Phase Transitions

This paper presents the magnetocaloric properties of polycrystalline La0.8– x Ag x Ca0.2MnO3 manganites (

Ferromagnetism in Zn 1– x Mn x O Nanoparticles Prepared by Ball Milling

x = 0.0

Magnetocaloric effect and the change from first- to second-order magnetic phase transition in Pr0.7CaxSr0.3-xMnO3 polycrystalline compounds

, 0.05, and 0.1) prepared by solid-state reaction. The results reveal that an Ag-concentration increase leads to a slight increase of the Curie temperature (

Critical Behavior and Magnetocaloric Effect in La 2 NiMnO 6 Nanocrystals

T_{C})

Influence of Crystallite Size on Magnetocaloric Effect and Critical Behavior La 0.7 Sr 0.3 Mn 0.92 Co 0.08 O 3 Nanoparticles

, and broadens the ferromagnetic–paramagnetic phase-transition region. The temperature dependences of the magnetic entropy change,

Large Magnetocaloric Effect Around Room Temperature in Double-Exchange Ferromagnets Pr 1– x Sr x MnO 3 With Short-Range Interactions

\Delta S_{m}(T)

An Effective Route to Control the Magnetic-Phase Transition and Magnetocaloric Effect of La 0.7 Ca 0.3 MnO 3 Nanoparticles

, for the samples have also been calculated using Maxwell’s relation. As a function of temperature,

First-to-second-order magnetic-phase transformation in La0.7Ca0.3-xBaxMnO3 exhibiting large magnetocaloric effect

-\Delta S_{m}(T)