Showing papers by "J. S. Gardner published in 2014"
TL;DR: In this paper, the linear and nonlinear ac susceptibility measurements of Yb-pyrochlores, Yb${}_{2}{X}-2}$O${}-7}$ ($X=\text{Sn}$, Ti, and Ge), show transitions with a ferromagnetic nature at 0.13 and 0.25 K, respectively, for Yb
Abstract: The linear and nonlinear ac susceptibility measurements of Yb-pyrochlores, Yb${}_{2}{X}_{2}$O${}_{7}$ ($X=\text{Sn}$, Ti, and Ge), show transitions with a ferromagnetic nature at 0.13 and 0.25 K for Yb${}_{2}$Sn${}_{2}$O${}_{7}$ and Yb${}_{2}$Ti${}_{2}$O${}_{7}$, respectively, and an antiferromagnetic ordering at 0.62 K for Yb${}_{2}$Ge${}_{2}$O${}_{7}$. These systematical results (i) provided information about the nature of the unconventional magnetic ground state in Yb${}_{2}$Ti${}_{2}$O${}_{7}$; (ii) realized a distinct antiferromagnetic ordering state in Yb${}_{2}$Ge${}_{2}$O${}_{7}$; and (iii) demonstrated that the application of chemical pressure through the series of Yb-pyrochlores can efficiently perturb the fragile quantum spin fluctuations of the Yb${}^{3+}$ ions and lead to very different magnetic ground states.
44 citations
TL;DR: In this paper, a cubic pyrochlore was prepared under high-pressure and high-temperature conditions and its magnetic ground state was investigated by measurements of specific heat, dc and ac magnetic susceptibility as functions of temperature, pressure, and magnetic field.
Abstract: A cubic ${\text{Er}}_{2}$${\text{Ge}}_{2}$${\text{O}}_{7}$ pyrochlore was prepared under high-pressure and high-temperature conditions and its magnetic ground state was investigated by measurements of specific heat, dc and ac magnetic susceptibility as functions of temperature, pressure, and magnetic field. We found that ${\text{Er}}_{2}$${\text{Ge}}_{2}$${\text{O}}_{7}$ undergoes a long-range antiferromagnetic transition at ${T}_{N}$ \ensuremath{\approx} 1.4 K, which can be further enhanced by applying external physical pressure. On the other hand, application of external magnetic fields suppresses the antiferromagnetic order to zero temperature around ${H}_{c}$ \ensuremath{\approx} 2.3 T, where a magnetic-field-induced spin-flop transition was observed. ${H}_{c}$ increases accordingly with increasing ${T}_{N}$ under external pressure. A comparison of the magnetic ground states and structural variations along the isostructural series ${\text{Er}}_{2}$${B}_{2}$${\text{O}}_{7}$ ($B$ = Sn, Ti, Ge) together with the high-pressure study on ${\text{Er}}_{2}$${\text{Ge}}_{2}$${\text{O}}_{7}$ indicated that the magnetic properties of these highly frustrated XY pyrochlore antiferromagnets are very sensitive to the minute structural changes that determine the anisotropic exchange interactions and the local crystal-electric-field environments of Er${}^{3+}$ ions.
19 citations
TL;DR: In this article, the authors present experimental results for the heavy-electron compound (CeCu) which show that it possesses short-range magnetic correlations down to a temperature of $T = 0.1$ K.
Abstract: We present experimental results for the heavy-electron compound ${\mathrm{CeCu}}_{4}\mathrm{Ga}$ which show that it possesses short-range magnetic correlations down to a temperature of $T=0.1$ K. Our neutron scattering data show no evidence of long-range magnetic order occurring despite a peak in the specific heat at ${T}^{*}=1.2$ K. Rather, magnetic diffuse scattering occurs which corresponds to short-range magnetic correlations occurring across two unit cells. The specific heat remains large as $T\ensuremath{\sim}0$ K, resulting in a Sommerfeld coefficient of ${\ensuremath{\gamma}}_{0}=1.44(2)$ J/mol ${\mathrm{K}}^{2}$, and, below ${T}^{*}$, the resistivity follows ${T}^{2}$ behavior and the ac magnetic susceptibility becomes temperature independent. A magnetic peak centered at an energy transfer of ${E}_{\mathrm{c}}=0.24(1)$ meV is seen in inelastic neutron scattering data which shifts to higher energies and broadens under a magnetic field. We discuss the coexistence of large specific heat, magnetic fluctuations, and short-range magnetic correlations at low temperatures and compare our results to those for materials possessing spin-liquid behavior.