Abstract
Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO6 powder sample have been investigated by X-ray diffraction (XRD), magnetic and electrical measurements. Our sample has been synthesized using the ceramic method. Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that our sample exhibits a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature TC is found to be 320 K. Arrott plots show that all our double-perovskite oxides exhibit a second-order magnetic phase transition. From the measured magnetization data of an LaNaMnMoO6 sample as a function of the magnetic applied field, the associated magnetic entropy change |−ΔSM| and the relative cooling power (RCP) have been determined. In the vicinity of TC, |−ΔSM| reached, in a magnetic applied field of 8 T, a maximum value of ∼4 J kg−1 K−1. Our sample undergoes a large magnetocaloric effect at near-room temperature. Resistivity measurements reveal the presence of an insulating-metal transition at Tρ = 180 K. A magnetoresistance of 30% has been observed at room temperature for 6 T, significantly larger than that reported for the A2FeMoO6 (A = Sr, Ba) double-perovskite system.
Highlights
Perovskite and double-perovskites oxides with general formula ABO3 and A2B B O6 respectively
Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO6 powder sample have been investigated by X-ray diffraction (XRD), magnetic and electrical measurements
Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group
Summary
Perovskite and double-perovskites oxides with general formula ABO3 and A2B B O6 respectively It is known that FeO6 and MoO6 octahedra are alternately ordered in a rock-salt lattice and the angle of the Fe–O–Mo chain is nearly 180° This oxide is a half metal and shows a ferrimagnetic ordering behaviour at low temperature with a high ordering temperature TC ∼ 420 K, in which spins at the Fe3+(3d5) and Mo5+(4d1) ions are aligned in the opposite direction. The availability of four distinct cation sites in A A B B O6 opens the door to the design of magnetic materials with novel topologies Compounds with this ordered double-perovskite-type show the potential for multiferroic behaviour. We report a giant magnetoresistance and moderate MCE over a broad temperature range
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