Vortex redistribution below the first-order transition temperature in the beta-pyrochlore superconductor KOs2O6.
A miniature Hall-sensor array was used to detect magnetic induction locally in the vortex states of the beta-pyrochlore superconductor KOs2O6. Below the first-order transition at T{p} approximately 8 K, which is associated with a change in the rattling motion of K ions, the lower critical field and the remanent magnetization both show a distinct decrease, suggesting that the electron-phonon coupling is weakened below the transition. At high magnetic fields, the local induction shows an unexpectedly large jump at T{p} whose sign changes with position inside the sample. Our results demonstrate a novel redistribution of vortices whose energy is reduced abruptly below the first-order transition at T{p}.
Shibauchi
T
T
Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan and Laboratoire des Solides Irradiés, Ecole Polytechnique, 91128 Palaiseau Cedex, France.
Konczykowski
M
M
van der Beek
C J
CJ
Okazaki
R
R
Matsuda
Y
Y
Yamaura
J
J
Nagao
Y
Y
Hiroi
Z
Z