The internal magnetism introduced by the magnetic nanoparticles combined with the external magnetic field can provide an effective way to modulate the thermoelectric (TE) properties of materials. Herein, we comparably investigate the effect of magnetism of Fe 3 O 4 nanoparticles (Fe 3 O 4 -NPs) and the external magnetic field on the cryogenic thermoelectric properties of Fe 3 O 4 -NP/Bi 0.85 Sb 0.15 nanocomposites. With the ferromagnetism−superparamagnetism transition, the Fe 3 O 4 -NPs in the superparamagnetic state exhibit a stronger magneto-trapped carrier effect, where the electron concentration at high temperature is evidently reduced. With the simultaneous increase of S and reduction of electronic thermal conductivity, a high ZT value of 0.33 at 180 K is obtained for 0.05 wt % Fe 3 O 4 /Bi 0.85 Sb 0.15 . Meanwhile, under the external magnetic field, the magnetoresistance of the composites is suppressed by Fe 3 O 4 -NPs, which results in a remarkable enhancement of the electronic transport performance. Consequently, the highest ZT value of 0.48 at 220 K under 1 T is achieved for 0.1 wt % Fe 3 O 4 -NPs/Bi 0.85 Sb 0.15 , increased by 55% compared with that of the matrix. A single-leg device is prepared using 0.1 wt % Fe 3 O 4 -NP/Bi 0.85 Sb 0.15 nanocomposites. Its cooling temperature difference at 180 K reaches 1.3 and 3.2 K under 0 and 1 T when applying 300 mA current, increased by 20 and 46% compared with that of the matrix, respectively. This work suggests that magnetism modulation with introducing magnetic nanoparticles will enhance the TE and magneto-TE performance of composite materials.

Bi1− xSb x alloys with large linear magnetoresistance (LMR) are a promising candidate for magneto-electronic devices. In this work, the highly (00 l) textured Bi1− xSb x (0 ≤  x ≤ 0.04) ribbons with nano-sized lamellar grains were prepared by the melt spinning method and their magneto-transport properties were investigated. All the ribbons exhibit obvious LMR features, and the crossover magnetic field ( Bc) from quadratic to linear magnetoresistance is remarkably reduced by Sb doping. Compared with the Bc of the x = 0 ribbon (about 1.28 T at 300 K), the Bc values of the Sb doped ribbons are significantly smaller, especially for the Bc of the x = 0.03 ribbon (only about 0.53 T at 300 K). Besides, for the x = 0.03 ribbon, the parameter Φ (MR%( B = 1 T)/ Bc) relevant to LMR performance reaches up to 52 at 300 K. Analysis of the LMR reveals that Sb doping makes the LMR mechanism transition from recombination of carriers for x = 0 ribbon to spatial fluctuation of carrier mobility governed LMR for x = 0.03 ribbon. This work is instructive to understand the transport features of textured Bi1− xSb x ribbons.