Study of the Structure, Magnetic, Thermal and Electrical Characterisation of ZnCr(2)Se(4): Ta Single Crystals Obtained by Chemical Vapour Transport

The new series of single-crystalline chromium selenides, Ta-doped ZnCr(2)Se(4), was synthesised by a chemical vapour transport method to determine the impact of a dopant on the structural and thermodynamic properties of the parent compound. We present comprehensive investigations of structural, electrical transport, magnetic, and specific heat properties. It was expected that a partial replacement of Cr ions by a more significant Ta one would lead to a change in direct magnetic interactions between Cr magnetic moments and result in a change in the magnetic ground state and electric transport properties of the ZnCr(2−x)Ta(x)Se(4) (x = 0.05, 0.06, 0.07, 0.08, 0.1, 0.12) system. We found that all the elements of the cubic system had a cubic spinel structure; however, the doping gain linearly increased the ZnCr(2)(−x)Ta(x)Se(4) unit cell volume. Doping with tantalum did not significantly change the semiconductor and magnetic properties of ZnCr(2)Se(4). For all studied samples (0 ≤ x ≤ 0.12), an antiferromagnetic order (AFM) below T(N)~22 K was observed. However, a small amount of Ta significantly reduced the second critical field (H(c2)) from 65 kOe for x = 0.0 (ZnCr(2)Se(4) matrix) up to 42.2 kOe for x = 0.12, above which the spin helical system changed to ferromagnetic (FM). The H(c)(2) reduction can lead to strong competition among AFM and FM interactions and spin frustration, as the specific heat under magnetic fields H < H(c)(2) shows a strong field decrease in T(N).