Caracterização estrutural e investigação do efeito exchange bias espontâneo na perovskita dupla La1,5Sr0,5CoMn0,5Fe0,5O6
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2021-02-26
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Universidade Federal de Goiás
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In this work we describe the synthesis and characterization of the structural, eletronic and magnetic properties of La1.5Sr0.5CoMn0.5Fe0.5O6 compound. Our main focus was on the investigation of 50% of Mn to Fe substitution in La1.5Sr0.5CoMnO6, with a particular interest in the spontaneous exchange bias effect, a phenomena characterized by the shift in the magnetic hysteresis curves taken after the system bein cooled in zero magnetic field.
The polycrystalline sample here investigated was syntesized by conventional solid state reaction technique and investigated by means of X-ray powder diffraction, magnetization as a function of temperature [M(T)] and magnetization as a function of magnetic field [M(H)]. The La1.5Sr0.5CoMn0.5Fe0.5O6 crystal forms in rhombohedral symmetry, space group, in agreement with results observed for similar compounds. The M(T) measurements have revealed a ferromagnetic-like transition at TC ≈ 150 K, and also indicated the presence of competing magnetic phases, which leads to the formation of ferromagnetics clusters embedded in a paramagnetic matrix at high temperature. This is a hallmark of the Griffiths Phase, here occurring in the 150 K < T < 205 K range. The M(H) curves carried after cooling the system in zero field have showed that La1.5Sr0.5CoMn0.5Fe0.5O6 exhibits the spontaneous Exchange Bias effect at low temperatures, while for the measurements carried after cooling the system in the presence of a external magnetic field it is observed a significant enhancement of the shift in the M(H) curve.
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SILVA, A. G. Caracterização estrutural e investigação do efeito exchange bias espontâneo na perovskita dupla La1,5Sr0,5CoMn0,5Fe0,5O6. 2021. 90 f. Dissertação (Mestrado em Física) - Universidade Federal de Goiás, Goiânia, 2021.