Microscopic study on spin state of nano-particles of antiferromagnet: ND4MnF3

Abstract

Abstract The magnetic behavior of small size grains of antiferromagnet of ND 4 MnF 3 with 30 nm diameter is particularly compared with that of bulk. To elucidate the low temperature property of a magnetic nano-particle, we characterized bulk sample of ND 4 MnF 3 , nano-particle of ND 4 MnF 3 with ca. 30 nm diameter, and magnetically diluted compound of ND 4 Mn 0.5 Zn 0.5 F 3 in bulk with using powder X-ray diffractometry, scanning electron microscopy (SEM), SQUID magnetometry, and particularly with solid-state deuterium NMR. The magnetic properties of these materials are discussed from the difference of magic angle spinning deuterium NMR spectra in the paramagnetic phase and from internal magnetic field determined by deuterium NMR spectra in the antiferromagnetic phase. It was found that critical behavior of the nano-particles with approaching the Neel temperature is clearly different from the bulk sample, while internal magnetic field of the nano-particles in the low temperature limit is almost the same as that of bulk sample. Near-surface spins of nano-particles in the antiferromagnetic phase were distinguished from the inner spins by wide-line deuterium NMR spectrum.