Structure and magnetic properties of theHo2Ge2O7pyrogermanate

Abstract

We report the anisotropic magnetic properties of Ho 2 Ge 2 O 7 determined from dc and ac magnetization, specific heat and powder neutron diffraction experiments. The magnetic lanthanide sublattice, seen in our refinement of the tetragonal pyrogermanate crystal structure, is a right-handed spiral of edge-sharing and corner-sharing triangles; the local Ho-O coordination indicates that the crystal field is anisotropic. Susceptibility and magnetization data indeed show that the magnetism is highly anisotropic, and the magnetic structure has the Ho moments

Magnetothermodynamics of the Ising antiferromagnetDy2Ge2O7

“…This is consistent with the spiral magnetic spin configuration determined from neutron diffraction experiments on Ho 2 Ge 2 O 7 [21]. Increasing the value of the applied field significantly reduces this peak due to the suppression of the antiferromagnetic long range order.…”

“…Similar results reported for isostructural Ho 2 Ge 2 O 7 [21] are believed to be due to the strong crystal electric field anisotropy. In Fig.…”

“…Single crystal and polycrystalline powder Dy 2 Ge 2 O 7 samples were prepared using flux growth and standard solid-state synthesis techniques respectively [21], and all results reported were qualitatively consistent between the two types of samples. Powder X-ray diffraction confirmed all samples to be single phase and to have a tetragonal structure.…”

“…Fig. 1(a) shows the rare earth lattice structure with the crystallographic axes marked (c-axis is along the [001] direction) [21]. DC magnetization measurements were performed using a Quantum Design Superconducting Quantum Interference Device (SQUID) magnetometer.…”

Frustration under pressure: Exotic magnetism in new pyrochlore oxides

“…High pressures are essential for the stabilization of these new pyrochlores, which tend to form lower symmetry structures under ambient pressure (such as the tetragonal pyrogermanate Ho 2 Ge 2 O 7 ). 33 Spin ices have held the attention of condensed matter physicists and solid state chemists alike for over a decade. 2,5 While the original mapping of the proton ordering in water ice was first put forward by Pauling and others, the first connection to spin disorder in pyrochlores was made by Anderson.…”