Of Lafeo <sub> 3 </ Sub> Nano-magnetic Materials Electric Quadrupole Hyperfine Interaction Of Pac Research

Perovskite LaFeO3 nano-magnetic material that shows a variety of unusual and interesting electronic, magnetic and structural properties is a new important magnetic material. Ideal LaFeO3 possesses a cubic structure, and La and Fe occupy a body center site with twelve-fold oxygen coordination and an octahedral site with six-fold oxygen coordination, respectively. This ideal cubic structure is distorted by size mismatch of large La and small Fe atoms. The distorted structure is mostly orthorhombic or rhombohedral. Any tiny alteration of crystal structure causes a change of the electric field gradient (EFG) exerted on La. Therefore, the measurement of the quadropole interaction of La with EFG can yield information on the change of crystal structure. The crystal structure of nano-materials and its variation with grain size is a currently interesting topic. In the present work the perturbed angular correlation is used to investigate the quadrupole interaction and micro-structure for the perovskite LaFeO3 nano-magnetic materials, and the comparison is made of the micro-structure between the LaFeO3 nano- and crystalline magnetic materials and between the LaFeO3 nano- magnetic materials with different grain size. The main research results are as follows:1, a sol-gel method is employed to prepare all the LaFeO3 samples used in the experiment.2, the perturbed angular correlation measurements are performed at room temperature for the 20 nm and 40 nm nano-LaFeO3 and crystalline LaFeO3. Only one electric quadrupole interaction is detected for each material, which is assigned to the La site. The quadrupole interaction frequencies are 687.4Mrad7s, 698.3Mrad/s and 742.9Mrad/s with a distribution coefficient of 0.014, 0.009 and 0.001, respectively. The fitting yields an EFG asymmetry parameter = 0. The experimental results show that a) the principal axis of the EFG is aligned with the crystallographic axis, b) the structure of the nano- and crystalline LaFeO3 is rhombohedral, and there is a tendency that the structures from the crystalline LaFeO3 to the nano- LaFeO3 and with the decreasing of the nano-grain size evolve towards the orthorhombic structure, and c) the frequency distribution coefficient increases with the decreasing of the nano-grain size and the crystalline LaFeO3 arrives at its minimum.3, a DEPAC dada processing program is imported from Uppsala University, and installed and used in the experimental data analyses, which makes the obtained data more reliable and accurate.