title: YbRh2Si2: spin fluctuations in the vicinity of a quantum critical point at low magnetic field.
abstract: We report a 29Si NMR study on aligned single crystals of YbRh2Si2 which shows behavior characteristic of a quantum critical point (QCP: T(N)-->0). The Knight shift K and the nuclear spin-lattice relaxation rate 1/T(1) of Si show a strong dependence on the external field H, especially below 5 kOe. At the lowest H used in this measurement (H approximately 1.5 kOe), it was found that 1/T(1)T continues to increase down to 50 mK, whereas K stays constant with a large magnitude below 200 mK. This result strongly suggests the development of antiferromagnetic fluctuations with finite q vectors that compete with q=0 spin fluctuations in the vicinity of the QCP near H=0.5 kOe.
authors.affiliation: Department of Physical Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ishida
authors.forename: K
authors.initials: K
authors.lastname: Okamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Kawasaki
authors.forename: Y
authors.initials: Y
authors.lastname: Kitaoka
authors.forename: O
authors.initials: O
authors.lastname: Trovarelli
authors.forename: C
authors.initials: C
authors.lastname: Geibel
authors.forename: F
authors.initials: F
authors.lastname: Steglich