Jörg Persson

Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystals

Magnetoresistance (MR) has attracted tremendous attention for possible technological applications. Understanding the role of magnetism in manipulating MR may in turn steer the searching for new applicable MR materials. Here we show that antiferromagnetic (AFM) GdSi metal displays an anisotropic positive MR value (PMRV), up to ~415%, accompanied by a large negative thermal volume expansion (NTVE). Around TN the PMRV translates to negative, down to ~−10.5%. Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5d bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4f spins. Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices.

Absence of magnetic ordering in the ground state of a SrTm2O4 single crystal

crystallographic sites. An appreciable deviation from the Brillouin function is visible above ˘8.3 T,indicating that Zeeman splitting of the high-level J-multiplets may lead to a new ground state. Oursingle-crystal polarized neutron scattering at ˘65 mK and powder unpolarized neutron di ractionat ˘0.5 K show no evidence for a long-range magnetic order and even detect no sign of di usemagnetic neutron scattering. The data re nements reveal that the two TmO