Ferromagnetic properties of ZnO:Mn nanocrystals obtained by the freeze-drying method

Abstract

In the work, the nanocrystals ZnO and ZnO:Mn with a concentration of Mn 2 and 4 at.% were obtained by the low-temperature freeze-drying method. For this purpose, solutions of zinc acetate Zn(CH3COO)2∙2H2O and manganese one Mn(CH3COO)2∙4H2O were used. By means of XRD, it is established that nanocrystals (NC’s) have a pure phase and wurtzite-type hexagonal lattice, their size is d ~ 65 nm. The EPR spectra of the samples have a broad absorption line. It is due to the presence of a large number of intrinsic and impurity defects in the NC’s. These defects are the result of the destructive action of hydrogen, which is a product of the thermal decomposition of zinc and manganese acetates. It is shown that there is a relationship between the number of crystal lattice defects in the ZnO:Mn NC’s and their ferromagnetic properties at room temperature. Samples of ZnO:Mn with a concentration of Mn 2 and 4 at.%. have a specific magnetization value of Мs equal to 0.089 and 0.045 emu/g, respectively. The results can have great potential in spintronic devices and spin-based electronics.

Dependence of Magnetic Properties of ZnO:Mn Nanocrystals on Synthesis Conditions

“…% was sprayed on droplets with d  20÷100 µm, which were then frozen in liquid nitrogen. Drying of the obtained cryogranules was carried out in a freeze-drier for 16 h [7]. The synthesis of NCs occurred at thermal decomposition of dry salts of zinc and manganese acetate at 350 °C.…”