arXiv subjects

Toshihiro Nomura

Publications and source records attributed to Toshihiro Nomura.

20 records · Page 2Linked to original sources

arXiv2016

Irreversible Heating Measurement with Microsecond Pulse Magnet: Example of the alpha-theta Phase Transition of Solid Oxygen

Dissipation inevitably occurs in first order phase transitions, leading to the irreversible heating. Conversely, the irreversible heating effect could be a clue for the first order phase transition. We measured the temperature change at the magnetic-field-induced alpha-theta phase transition of solid oxygen. The significant temperature increase from 13 to 37 K, amounting to 700 J/mol, is observed due to the irreversible heating at the first order phase transition. We argue that the hysteresis loss of the magnetization curve and the dissipative structural transformation account for the irreversible heating. The measurement of the irreversible heating can be utilized for detecting the first-order phase transition in good combination with the ultrahigh magnetic fields generated in microseconds.

cond-mat.mtrl-sci↗

arXiv2016

Spin state ordering of strongly correlating LaCoO$_{3}$ induced at ultrahigh magnetic fields

Magnetization measurements of LaCoO$_{3}$ have been carried out up to 133 T generated with a destructive pulse magnet at a wide temperature range from 2 to 120 K. A novel magnetic transition was found at $B>100$ T and $T>T^{*}=32\pm 5$ K which is characterized by its transition field increasing with increasing temperature. At $T<T^{*}$, the previously reported transition at $B\sim65$ T was observed. Based on the obtained $B$-$T$ phase diagram and the Clausius-Clapeyron relation, the entropy of the high-field phase at 80 K is found to be smaller for about $1.5$ J K$^{-1}$ mol$^{-1}$ than that of the low-field phase. We suggest that the observed two high-field phases may originate in different spatial orders of the spin states and possibly other degrees of freedom such as orbitals. An inherent strong correlation of spin states among cobalt sites should have triggered the emergence of the ordered phases in LaCoO$_{3}$ at high magnetic fields.

cond-mat.str-el↗