Quantum tunneling of magnetization in GaN:Mn nanoparticles

Abstract

GaN:Mn nanoparticles were synthesized successfully by DC arc discharge plasma without any catalyst or template. X-ray diffraction patterns revealed that all peaks position of GaN:Mn nanoparticles were shifted towards larger angles, indicating the c lattice parameter of GaN:Mn is smaller than that of GaN due to the lattice distortion. The growth mechanism explains the characteristic of morphology and size. The room temperature photoluminescence (PL) of GaN:Mn nanostructure exhibits a relatively broad range of visible light absorption due to dopant-induced energy levels within the band gap increasing the yield for electron–hole pair formation under illumination with visible light. The magnetic properties were investigated by VSM and quantum design MPMS SQUID. Mn doped GaN nanoparticles show two prominent critical points corresponding to the magnetic phase transition, respectively. One is the classical thermally driven from superparamagnetic (SP) to blocked SP, the other is the quantum tunneling of magnetization from magnetic long-range order to quantum superparamagnetic (QSP) state. The magnetism is derived from the Mn atoms, the magnetic coupling between Mn atoms depends on the mediating of N.