Resonance Indirect Exchange Interactions between Localized Spin States in 3D Dirac semimetal

Earlier [1] by the ESR method it was found that the placement of impurity europium ions in α - Cd3As2 [2] occurs in two crystallographic positions - the position of substitution of cadmium ions and the position of implantation. At high temperatures, for both positions, linear (pseudo-Corringa) dependences of the ESR line width and position were observed. The aforementioned crystallographic positions in the anti-fluorite-type lattice are practically identical in terms of crystallographic symmetry, but differ in the degree of chemical compression. The report examines the effect of chemical compression on the formation of donor electrons. In the compressed state, the bivalent europium ion is inclined, donating an electron to the conduction band, to pass into the trivalent state with a smaller ionic radius. This reduces the degree of chemical compression and response stresses in the crystal lattice. However, the presence of europium in a nonmagnetic trivalent state occurs only for a small part of the time and leads to a decrease in the effective local magnetic moment on the europium ion [3]. A change in the degree of chemical compression with a change in temperature explains the observed [1] temperature dependences of the position and width of the ESR line, the values of g - factors (g ~ 2.2 and g ~ 4.4.) of Eu2+ impurity ions. The values of g-factors (g ~ 10-15) of conduction electrons are determined. It can be seen from the temperature behavior of the ESR lines that these two spin ensembles are ordered at different temperatures, which indicates the existence of a crystallographic position-selective indirect exchange [4] interaction of Eu2+ spins by donor conduction electrons. A mechanism is proposed for selective indirect exchange interaction between magnetic impurities and spin diffusion in thus subsystems. The selectivity of interactions consists in the fact that interact with each other the impurities located at the crystal lattice nodes which have the same local symmetry.

Reference:
[1] Yu. V. Goryunov, A. N. Nateprov, Phys.Sol. St., 60, 68 (2018).
[2] S. Borisenko, Q. Gibson, et al., Phys. Rev. Lett. 113, 027603 (2014).
[3] R. K. Wangsness, Phys.Rev. 91, 1085 (1953)
[4] Hao-Ran Chang, Jianhui Zhou, et al., Phys. Rev. B 92, 241103(R) (2015)