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Nanostructure and magnetic properties of the MnZnO system, a room temperature magnetic semiconductor?
|Authors:||Costa Krämer, José Luis ; Briones Fernández-Pola, Fernando ; Fernández Lozano, José Francisco ; Caballero Cuesta, Amador ; Villegas, Marina; Díaz Muñoz, Marcos ; García, Miguel Ángel Pérez; Hernando, Antonio|
Surfaces, interfaces and thin films
Condensed matter: electrical, magnetic and optical
|Publisher:||Institute of Physics Publishing|
|Citation:||Nanotechnology 16(2): 214-218 (2005)|
|Abstract:||The magnetic properties of the system MnZnO prepared by conventional ceramic procedures using ZnO and MnO2 starting powders are studied and related to the nanostructure. Thermal treatment at 500 °C produces a ferromagnetic phase, although this temperature is not high enough to promote proper sintering; thus the thermally treated compact shows brittle characteristics of unreacted and poorly densified ceramic samples. Scanning electron microscopy and x-ray analysis reveal the appearance of a new phase, most probably related to the diffusion of Zn into MnO2 oxide nanocrystals. The magnetic properties deviate considerably from what would be expected of an unreacted mixture of ZnO (diamagnetic) and MnO2 particles (paramagnetic above 100 K and anti-ferromagnetic below that temperature), exhibiting a ferromagnetic like behaviour from 5 to 300 K and beyond mixed with a paramagnetic component. The ferromagnetic phase seems to be originated by diffusion at the nanoscale of Zn into MnO2 grains. The Curie temperature of the ferromagnetic phase, once the paramagnetic component has been subtracted from the hysteresis loops, is measured to be 450 K. EPR resonance experiments from 100 to 600 K confirm a ferromagnetic to paramagnetic like transition above room temperature for these materials.|
|Publisher version (URL):||http://dx.doi.org/10.1088/0957-4484/16/2/006|
|Appears in Collections:||(IMN-CNM) Artículos|
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