Marcus C. Bennett

Yb2Pt2Pb: Magnetic frustration in the Shastry-Sutherland lattice

Here, we have synthesized single crystals of Yb2Pt2Pb, which crystallize in the layered U2Pt2Sn-type structure, where planes of Yb ions lie on a triangular network. Here, we report the results of magnetization, specific heat, and electrical resistivity experiments. The lattice constants and high temperature magnetic susceptibility indicate that the Yb ions are trivalent, while the Schottky peaks in the specific heat show that the ground state is a well isolated doublet. A significant magnetic anisotropy is observed, with the ratio of susceptibilities perpendicular and parallel to the magnetic planes differing by as much as a factor of 30 at the lowest temperatures. Antiferromagnetic order occurs at a Neel temperature TN = 2.07 K. Evidence of short range magnetic fluctuations is found in the magnetic susceptibility and electrical resistivity, which have broad peaks above TN, and in the slow development of the magnetic entropy at TN. Our experiments indicate that Yb2Pt2Pb is a quasi-two-dimensional and localized moment system, where strong magnetic frustration may arise from the geometry of the underlying Shastry-Sutherland lattice.

Magnetotransport in single-crystal half-Heusler compounds

We present the results of electrical resistivity and Hall effect measurements on single crystals of HfNiSn, TiPtSn, and TiNiSn. Semiconducting behavior is observed in each case, involving the transport of a small number of highly compensated carriers. Magnetization measurements suggest that impurities and site disorder create both localized magnetic moments and extended paramagnetic states, with the susceptibility of the latter increasing strongly with reduced temperature. The magnetoresistance is sublinear or linear in fields ranging from

Magnetic Field Tuning of Antiferromagnetic Yb3Pt4

0.01\char21{}9\phantom{\rule{0.3em}{0ex}}\mathrm{T}

Weak ferromagnetism in CaB6

at the lowest temperatures. As the temperature increases, the normal quadratic magnetoresistance is regained, initially at low fields, and at the highest temperatures extending over the complete range of fields. The origin of the vanishingly small field scale implied by these measurements remains unknown, presenting a challenge to existing classical and quantum mechanical theories of magnetoresistance.

The ground state of a quantum critical system: Neutron scattering on Ce(Ru1-xFex)2Ge2.

We present measurements of the specific heat, magnetization, magnetocaloric effect and magnetic neutron diffraction carried out on single crystals of antiferromagnetic Yb

Ferromagnetism, superconductivity and secondary phases in the dilute magnetic semiconductor Pt1−xRExSb2 (RE = La, Ce, Gd, Yb)

_{3}

Structure, and magnetic and transport behavior of twinned Ce2Rh3(Pb,Bi)5

Pt

A new unconventional antiferromagnet, Yb3Pt4

_{4}

A new unconventional antiferromagnet, Yb3Pt4Yb3Pt4

, where highly localized Yb moments order at

Yb

T_{\rm N}=2.4