Manipulation of ferromagnetic ordering in magnetic semiconductor Li<sub>1.05</sub>(Zn<sub>0.925</sub>, Mn<sub>0.075</sub>)As by In doping

Abstract

Magnetic semiconductors (MSs) that can manipulate both spin degree of freedom and charge degree of freedom have become an important research field in semiconductor spintronics. In recent years, a new series of bulk form MSs, which are iso-structure to the iron-based superconductors were reported. In these new materials, spins and carriers are separately introduced, and can be precisely manipulated. Li(Zn,Mn)As with <i>T</i><sub>C</sub> ~50 K is the first bulk MS with spins and charges separated. The Li(Zn,Mn)As has <i>p</i>-type carriers, which is in contradiction with the theoretical calculation results by Mašek et al. who claimed that doping extra Li will induce <i>n</i>-type carriers. So, it is necessary to study the formation reason of hole carriers in Li(Zn,Mn)As and their effect on ferromagnetic ordering. In this work, a series of Li<sub>1.05</sub>(Zn<sub>0.925–<i>y</i></sub>,Mn<sub>0.075</sub> ,In<sub><i>y</i></sub>)As (<i>y</i> = 0, 0.05, 0.075, 0.1) new materials are successfully synthesized by introducing <i>n</i>-type carriers into the <i>p</i>-type bulk MS Li<sub>1.05</sub>(Zn<sub>0.925</sub>, Mn<sub>0.075</sub>)As through (Zn<sup>2+</sup>, In<sup>3+</sup>) substitution. Magnetization measurements reveal that all the samples still maintain a ferromagnetic transition signal similar to MS Li<sub>1.05</sub>(Zn<sub>0.925</sub>, Mn<sub>0.075</sub>)As, and the Curie temperature <i>T</i><sub>C</sub> is obviously suppressed with the increase of In-doping concentration. Clear hysteresis loops demonstrate the ferromagnetic ordering state. The resistivity increases gradually with the increase of In-doping concentration. Our results show that the (Zn<sup>2+</sup>, In<sup>3+</sup>) substitution successfully introduces n-type carriers into Li<sub>1.05</sub>(Zn<sub>0.925</sub>, Mn<sub>0.075</sub>)As, and the original p-type carriers into Li<sub>1.05</sub>(Zn<sub>0.925</sub>,Mn<sub>0.075</sub>)As, which are partial neutralized, resulting in the decrease of p-type carrier concentrations, which obviously suppresses the ferromagnetic ordering of Li(Zn,Mn)As. It reflects the important roles played by carriers in forming ferromagnetic ordering in MS materials. The fabrication of Li<sub>1.05</sub>(Zn<sub>0.925–<i>y</i></sub>, Mn<sub>0.075</sub>,In<sub><i>y</i></sub>)As material gives us a better understanding of the mechanism of ferromagnetic ordering in Li(Zn, Mn)As, and these results will be helpful in searching for more novel magnetic semiconductor materials.