Year: 2007
Type: article
Abstract: The isothermal magnetoresistance (MR) with magnetic field $(H)$ parallel and perpendicular to the $ab$ plane is systematically studied on the single crystal ${\mathrm{Na}}_{0.52}\mathrm{Co}{\mathrm{O}}_{2}$ with charge ordering at $\ensuremath{\sim}50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and an in-plane ferromagnetism below $25\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The isothermal MR behavior with $H\ensuremath{\Vert}ab$ plane and that with $H\ensuremath{\perp}ab$ plane are quite different. When $H\ensuremath{\Vert}ab$ plane, the MR is always negative and the in-plane ferromagnetic behavior is enhanced, while the MR with $H\ensuremath{\perp}ab$ plane changes from negative to positive with decreasing temperature or increasing $H$, and the in-plane ferromagnetic behavior is suppressed. A striking feature is that the MR with $H\ensuremath{\perp}ab$ plane shows a hysteresis behavior below $25\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, which is absent for the case of $H\ensuremath{\Vert}ab$ plane. These results provide strong evidence for a spin-flop transition of small moments of ${\mathrm{Co}}^{3.5\ensuremath{-}\ensuremath{\delta}}$ sites induced by $H\ensuremath{\perp}ab$ plane, leading to a metamagnetic transition for small moments of ${\mathrm{Co}}^{3.5\ensuremath{-}\ensuremath{\delta}}$ sites. Such complex magnetism suggests an unconventional superconductivity in ${\mathrm{Na}}_{x}\mathrm{Co}{\mathrm{O}}_{2}$ system because the charge-ordering ${\mathrm{Na}}_{x}\mathrm{Co}{\mathrm{O}}_{2}$ around $x=0.5$ has been considered to be the parent compound of superconductivity.
Source: Physical Review B
Institution: University of Science and Technology of China
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1980594915