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The effects of A-site cation size mismatch on La0.7 − xNdxCa0.3 − y(Ba,Sr)yMnO3 perovskite materials with a constant A-site average ionic radius ⟨rA⟩ = 1.2052 Å have been investigated. Polycrystalline samples have been prepared through the standard solid-state reaction method at high temperatures, and their structures, magnetic properties, and magnetocaloric effect (MCE) have been investigated in detail. X-ray diffraction patterns show that all of the samples crystallized in an orthorhombic structure with the space group Pnma. XPS analysis confirmed the Mn3+/Mn4+ ratio remained constant as σ2 was varied. Meanwhile, upon increasing σ2 from 0.0002 to 0.007, the Curie temperature (TC) decreased linearly from 254 K to 108 K. Based on M-H isotherms, Arrott plots and the maximum magnetic entropy prove a crossover of first-to-second-order transition with increasing σ2. Samples with σ2 = 0.0002, 0.001, and 0.003 exhibited a first-order transition and had larger MCEs than those showing a second-order transition. [ABSTRACT FROM AUTHOR]

In this paper, the effect of A-site ionic disorder (σ2) on the structure, magnetic and magnetocaloric properties in La 0.85-x Nd x Ag 0.15-y K y MnO 3 have been investigated. X-ray diffraction analysis using Rietveld refinement shows that the crystal structure of the perovskite manganites changes from rhombohedral (space group R3 ͞C) to orthorhombic (space group Pnma) structure with the increasing in σ2. Magnetization measurements showed that, upon increasing σ2, ferromagnetic double exchange interaction of the perovskite manganites diminishes, and as a result, Curie temperature (T C) of the samples decrease linearly. The inverse of susceptibility shows a downturn with decreasing temperature before T C indicating the existence of the Griffiths phase for La 0.62 Nd 0.23 Ag 0·099 K 0·051 MnO 3 (σ2 = 0.004). The magnetic phase transitions of all the samples are belongs to second order transition. [ABSTRACT FROM AUTHOR]

Series samples MnBi1-xGdx (x = 0, 0.04, 0.08, 0.12, and 0.16) were prepared and studied the structure and magnetic properties. The Rietveld refinement results showed that the low-temperature phase MnBi content in these samples is above 78% and the doped atoms occupied the position of Bi in the MnBi crystal structure. The Debye temperature is founding to decrease with increasing doping. The Curie temperature, paramagnetic to ferromagnetic transition temperature, thermal hysteresis, saturation magnetization, and coercive force of the samples change significantly with increasing doping content. Within a temperature range of 300–500 K, a positive coercivity temperature coefficient β existed. This work helps MnBi-Gd as a candidate for high-temperature magnetic material applications and contributes to the development of tailoring magnetic properties. [ABSTRACT FROM AUTHOR]

A Retraction Note to this paper has been published: https://doi.org/10.1007/s11051-021-05227-z [ABSTRACT FROM AUTHOR]

The effects of the substitution of La3+ by smaller rare-earth ion Nd3+ on the structural, magnetic and magnetocaloric properties of La 0.67-x Nd x Ca 0.13 Ba 0.2 MnO 3 (x = 0.02, 0.06, 0.1) manganites prepared by solid state sintering technology have been investigated. X-ray diffraction analysis shows that the x = 0.02 sample crystallizes in the rhombohedral structure with R 3 ¯ c space group symmetry and the x = 0.06, 0.1 samples belong to the orthorhombic structure with Ibmm space group. The Rietveld refinements for all samples were carried out to investigate on the crystal structures of the samples. Thermomagnetic measurements indicate that all the samples exhibit a magnetic transition from ferromagnetic to paramagnetic phase with increasing temperature. The Curie temperature T C systematically decreases from 308 K to 280 K with the accumulation of Nd concentration. Critical analysis demonstrates that the estimated critical exponents β, γ and δ are between the theoretically predicted values for 3D-Ising and mean-field theory models for all samples. The magnetic entropy change has been calculated from the isothermal magnetization measurements as a function of the applied magnetic field at various temperatures near T C. The maximum magnetic entropy change -ΔS max under an applied magnetic field of 1.6 T was found to be 3.06, 2.92 and 2.48 J kg−1 K−1 respectively for x = 0.02, 0.06 and 0.1 samples. This indicates that these manganites are remarkably potential functional materials working as magnetic refrigerants near room temperature. • The crystal structure of samples transform from rhombohedral to orthorhombic with the accumulation of Nd concentration. • The Curie temperature T C decreases from 308 K to 280 K with increasing Nd composition. • The estimated critical exponents β, γ and δ are in between the theoretically predicted values for 3D-Ising and mean-field theory models for all samples. • The largest value among the maximum magnetic entropy change −ΔS max of all samples under applied magnetic field of 1.6 T were found to be 3.06 J kg−1 K−1 for x = 0.02. [ABSTRACT FROM AUTHOR]

• The susceptibility of the compounds with RE = Sm and Gd-Dy exhibits an upturn below T N. • Due to spin-flip, the metamagnetic transitions are observed in REAgSb 2 (RE = Pr, Gd-Ho) compounds. • ΔS max of CeAgSb 2 and PrAgSb 2 under the applied magnetic field of 6 T are 5.1 and 7.9 J.kg−1.K−1, respectively. • The variation in the DOS of REAgSb 2 compounds are dominated by the RE 4f bands. Magnetic properties and electronic structure of REAgSb 2 compounds (RE = La-Nd, Sm and Gd-Er) were investigated by experimental measurements on their polycrystalline samples combining with first-principles calculation. X-ray powder diffraction analysis shows that all compounds crystallize in a tetragonal HfCuSi 2 -type structure (Space group P 4/ nmm , No. 129, tP8). The results of magnetic measurements reveal that LaAgSb 2 is non-magnetic, CeAgSb 2 is ferromagnetic, and other compounds are antiferromagnetic. The magnetic ordering temperatures were obtained by d M /d T plots, which are distributed between 3.2 and 14.2 K. According to Curie-Weiss law, it was found that the effective magnetic moments of these compounds are close to rare earth trivalent ions in REAgSb 2. The metamagnetic transitions are observed for REAgSb 2 (RE = Pr, Gd-Ho) according to M−H curves at 2 K. The Arrott plots reveal that the magnetic phase transition type belongs to second-order phase transition for REAgSb 2 (RE = Ce, Pr). The maximum magnetic entropy changes of CeAgSb 2 and PrAgSb 2 are measured to be 5.1 and 7.9 J.kg−1.K−1, respectively. The electronic structures of REAgSb 2 compounds have been studied based on density functional theory. The electronic structures data of REAgSb 2 suggest that the DOS dispersions are close to the RE 4f electrons and there is a strong correlation between RE and Sb atoms. The hybridization between RE 4f and Sb 5p electrons gradually increases as a function of atomic number for REAgSb 2 (RE = Ce-Sm, Gd), while gradually decreases for the other compounds. [ABSTRACT FROM AUTHOR]