Nested antiferromagnetic spin fluctuations and non-Fermi-liquid behavior in electron-doped CeCo
Ni
In
電子ドープ系CeCo
Ni
In
におけるネストした反強磁性スピン揺らぎと非フェルミ液体挙動
酒井 宏典
; 徳永 陽
; 神戸 振作
; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; 小手川 恒*; 藤 秀樹*; 鈴木 康平*; 大島 佳樹*; 横山 淳*
Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Zhu, J.-X.*; Ronning, F.*; Thompson, J. D.*; Kotegawa, Hisashi*; To, Hideki*; Suzuki, Kohei*; Oshima, Yoshiki*; Yokoyama, Makoto*
Ni置換系CeCo
Ni
In
について、核四重極共鳴と核磁気共鳴(NQR/NMR)を用いて調べた。
=2.3Kの超伝導転移gは、Ni置換によって徐々に下がってゆき、
=0.25の時にゼロとなる。超格子を用いた密度関数計算によってNQRスペクトルの帰属を行い、スピン格子緩和率
が一様に抑えられ、反強磁性スピン揺らぎがNi置換によって弱められることを明らかにした。
=0.25のとき、
が、
=2Kで極大を示すことがわかった。このことは、遍歴電子の反強磁性スピン揺らぎがネスティングによって打ち消し合っているとして理解できる。
We investigate the electronic state of Ni-substituted CeCo
Ni
In
by nuclear quadrupole and magnetic resonance (NQR/NMR) techniques. The heavy fermion superconductivity below
K for
is suppressed by Ni substitutions, and
reaches zero for
. The
In NQR spectra for
and 0.25 can be explained by simulating the electrical field gradient that is calculated for a virtual supercell with density functional theory. The spin-lattice relaxation rate
indicates that Ni substitution weakens antiferromagnetic correlations that are not localized near the substituent but instead are uniform in space. The temperature (
) dependence of
for
shows a maximum around
K and
decreases toward almost zero when temperature is further reduced as if a gap might be opening in the magnetic excitation spectrum; however, the magnetic specific heat and the static magnetic susceptibility evolve smoothly through
with a
dependence. The peculiar T dependence of
and non-Fermi-liquid specific heat and susceptibility can be interpreted in a unified way by assuming nested antiferromagnetic spin fluctuations in a quasi-two-dimensional electronic system.