Abstract
We present measurements of the basic properties ofCe2Ge2Mg,Yb2Pt2Pb andCe2Pt2Pb, which are members of a new class of geometrically frustrated magnetsR2T2X (R = rare earth,T = transition metal,X = main group). Here, themoment-bearing R atoms are confined to layers where they are arranged in the Shastry–Sutherlandlattice. Magnetic susceptibility and specific heat measurements indicate thatCe2Ge2Mg orders antiferromagneticallyat 9.4 K and Yb2Pt2Pb at 2.07 K. No long ranged order is observed inCe2Pt2Pb above 0.05 K. Analysis of Schottky peaks in the specific heat indicates that all threecompounds have doublet ground states that are well separated in energy from the excitedstates of the crystal-field-split manifold. Electrical resistivity measurements show thatCe2Ge2Mg andYb2Pt2Pb are excellent metals with small residual resistivities. However, the measured resistivity ofCe2Pt2Pb is large and almost temperature-independent, suggesting that strong disorder or perhapsstrong quantum critical fluctuations saturate the quasiparticle scattering in this compound.The magnetic entropy develops very slowly above the onset of antiferromagnetic order andwe discuss the possibility that a nonordered fluid of dimerized moments exists aboveTN inCe2Ge2Mg andYb2Pt2Pb, and for a wide rangeof temperatures in Ce2Pt2Pb, which appears to be close to a frustration-driven quantum critical point.
Published Version
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