1202.0220 (M. S. Kim et al.)

Spin Liquids and Antiferromagnetic Order in the
Shastry-Sutherland-Lattice Yb$_{2}$Pt$_{2}$Pb    [PDF]

M. S. Kim, M. C. Aronson

We present measurements of the magnetic susceptibility $\chi$ and the
magnetization M of single crystals of metallic \ypp, where localized Yb moments
lie on the geometrically frustrated Shastry-Sutherland Lattice (SSL). Strong
magnetic frustration is found in this quasi-two dimensional system, which
orders antiferromagnetically (AF) at T$_{N}$=2.02 \emph{K} from a paramagnetic
liquid of Yb-dimers, having a gap $\Delta$=4.6 \emph{K} between the singlet
ground state and the triplet excited states. Magnetic fields suppress the AF
order, which vanishes at a 1.25 \emph{T} quantum critical point. The spin gap
$\Delta$ persists to 1.5 \emph{T}, indicating that the AF degenerates into a
liquid of dimer triplets at T=0. Quantized steps are observed in M(B) within
the AF state, a signature of SSL systems. Our results show that \ypp is unique,
both as a metallic SSL system that is close to an AF quantum critical point,
and as a heavy fermion compound where geometrical frustration plays a decisive
role.

View original: http://arxiv.org/abs/1202.0220