Magnetothermopower and giant magnetoresistance in the spin-glass CuCrTiS4 thiospinel

Abstract

The transport properties of the thiospinel CuCrTiS4 have been investigated in detail, focusing on the possible interplay between charges and spins, and its consequence on transport, and more specifically on the thermoelectric properties. The chemical homogeneity of a CuCrTiS4 polycrystalline sample synthesized by a direct reaction of the constitutive elements has been carefully probed by X-ray diffraction and transmission electron microscopy techniques. This thiospinel exhibits below 75 K, in its paramagnetic regime, a variable range hopping (VRH) conduction, associated with a giant magnetoresistance (MR), which persists below the spin-glass transition temperature at 8 K, reaching -95% in 9 T at 5 K. All the MR data can be rescaled as a function of H/T and described using a Brillouin function with S = 3/2. This demonstrates that the paramagnetic fluctuations strongly impact the transport properties, and this is confirmed by the Seebeck coefficient which depends on the magnetic field at low temperature, with a large negative magnetothermopower (MTEP) effect of -26% at 20 K, i.e., the thermopower is reduced as the spin alignment reduces the spin entropy. This first report of MTEP in CuCrTiS4 shows that this thiospinel behaves rather similarly to strongly correlated oxides, with MR and MTEP enhanced in the case of VRH transport with paramagnetic spins, such as in cobalt misfits or colossal MR manganites.

Enhanced thermoelectric performance in polymorphic heavily Co-doped Cu2SnS3 through carrier compensation by Sb substitution

“…As shown in Figure 3(a and b) for the SEM images for thermally etched mirror surface of the merely Co-doped CTS and the x = 0.08 sample, respectively, no remarkable difference in grain growth has been found due to the Sb substitution. EDX mappings revealed homogeneous distribution of all elements, without preferential Sb segregation in the grains or to the grain boundaries, which suggests that the c- and t-CTS might have formed a very special microstructure that is possibly featured with nanoscale intergrowth or even more complicated nano-texture, which should resemble the one that we have revealed in Zn-doped CTS previously [ 14 ].

Figure 3.

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“…In particular, from the viewpoint of scalable commercial application, intensive efforts have been made in research of TE materials beyond the currently most-widely used heavy alloys, such as compounds of Te, Bi, Pb and etc., most of which are naturally scarce and/or toxic. Thus, a multitude of environmentally friendly thermoelectric sulphides has been reported, such as chalcopyrite CuFeS 2 [7,8], tetrahedrite [9,10], paracostibite CoSbS [11,12] and thiospinels [13][14][15].…”

Tailoring the thermoelectric and structural properties of Cu–Sn based thiospinel compounds [CuM1+xSn1−xS4 (M = Ti, V, Cr, Co)]

“…[29][30][31][32] Incidentally, some tellurides with spinel-related structures have also been found lately with relatively high thermoelectric performance. 33,34 Although some attractive themoelectric properties have been reported for thiospinel compounds in the family of the general composition CuM2S4, such as CuCo2S4, CuTi2S4, CuCr2S4 and their derivatives (where Co, Ti, Cr are partially substituted for each other), [29][30][31][32]35 not much information is available on the thermoelectric properties of Sn-based thiospinel compounds and their derivatives.…”

Structural Peculiarities and Thermoelectric Study of Iron Indium Thiospinel

“…The spinel structure is known to be flexible and allows an accommodation of 1) a variety of metallic elements with different atomic size and mass, 2) ordered or disordered arrangement of cations (so‐called normal, inverse, or intermediate structures), and 3) partially occupied crystallographic positions. All these result in a diversity of magnetic, optical, catalytic, electrical, as well as thermoelectric (TE) properties . Many spinels consisting of well‐abundant and environmental‐friendly elements (which is crucial for a possible thermoelectric application) became the object of numerous studies.…”