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INFLUENCE OF BALL MILLING PROCESS ON STRUCTURAL AND MAGNETIC PROPERTIES OF La0.7Sr0.3MnO3 MANGANITE

2014; EIA University; Volume: 11; Issue: 1 Linguagem: Inglês

10.24050/reia.v0i1.575

2463-0950

Gloria Campillo Figueroa, Óscar Arnache Olmos, Andrés Gil Garcés, Jaime Alberto Osorio Vélez, J. J. Beltrán, Eval Baca Miranda, R. Hernández Castillo,

Rare-earth and actinide compounds

This investigation presents the magnetic and structural properties of ferromagnetic manganite La0.7Sr0.3MnO3, (LSMO), subjected to ball milling processes. The LSMO powder sample was obtained by solid state reaction from high purity precursors. From x-ray diffraction (xRD), the sample showed the characteristic peaks of this phase. By means of thermogravimetric analysis (TGA) assisted by magnetic field, used as first method to measure the Curie temperature TC, the NM (non-milling) LSMO powders exhibited a TC=369.69 K (96.96 oC), which agrees with the magnetization measurements. In order to study size dependent properties, LSMO powder was subjected to mechanical milling pro- cesses during 3, 6 and 12 hours. From Rietveld refinement of xRD patterns, a reduction in crystallite average size (Dv) and a stabilization of crystalline structure (the R3c space group), with milling time (tM), were observed. These results are consistent with the Scanning Electron Microscopy (SEM) images, which showed more homogeneity in the grain distri- bution with longer milling times. From magnetic characterization results, it was found that the saturation magnetization decreases with decreasing grain size (smaller Dv). This behavior is attributed to surface effects that induce magnetically disordered states in smaller particle sizes. However, the TC is kept constant around 365 K and it is independent of tM. Abstract: Este trabajo estudia las propiedades estructurales y magneticas de la manganita La0,7Sr0,3MnO3 (LSMO) ob- tenida por el metodo de reaccion en estado solido y sometida a procesos de molienda mecanica. En las medidas de difraccion de rayos x, xRD, la muestra en polvo de LSMO presento los picos caracteristicos de esta fase. La tecnica de termogravimetria (TGA) asistida con campo magnetico, mostro una temperatura de Curie TC = 369,69 K (=96,96 oC). Este resultado concuerda con la temperatura de la transicion magnetica, cercana a 365 K. Con el fin de analizar la dependencia de las propiedades magneticas y estructurales en relacion con el tamano de particula, las muestras se sometieron a molienda mecanica por 3, 6 y 12 horas. A partir de refinamiento Rietveld de los rayos x, se observo una reduccion de tamano de particula y una estabilizacion de la estructura cristalina de grupo espacial R3c, a medida que aumenta el tiempo de molienda tM. Esto es consistente con las imagenes de SEM, que mostraron mas homogeneidad de la distribucion de tamano a mayor tM. En las medidas de magnetizacion en funcion de la temperatura, se encontro que la magnetizacion de saturacion decrece con la disminucion de tamano de grano (Dv pequenos). Este comportamiento es atribuido a estados magneticamente desordenados que se generan en la superficie. Sin embargo, la temperatura critica se mantiene constante alrededor de 365 K e independiente de tM.