Reentrant Phase Diagram of Yb2Ti2O7 in a

Allen Scheie

¹

,

J. Kindervater

²

,

Steffen Säubert

³

et al.

Abstract

We present a magnetic phase diagram of rare-earth pyrochlore Yb_{2}Ti_{2}O_{7} in a ⟨111⟩ magnetic field. Using heat capacity, magnetization, and neutron scattering data, we show an unusual field dependence of a first-order phase boundary, wherein a small applied field increases the ordering temperature. The zero-field ground state has ferromagnetic domains, while the spins polarize along ⟨111⟩ above 0.65 T. A classical Monte Carlo analysis of published Hamiltonians does account for the critical field in the low T limit. However, this analysis fails to account for the large bulge in the reentrant phase diagram, suggesting that either long-range interactions or quantum fluctuations govern low field properties.

Magnetic excitations in the ground state of Yb2Ti2O7

“…Reference [13] does not report detailed temperature dependence of the measured intensities, but it is supposed that it is only below the phase transition that the sample develops the all-in-all-out ferromagnetic order. Recent work [36] on a single crystal reports results in close resemblance to ours. Notwithstanding being performed using the intensities of only three Bragg peaks, the magnetic structure refinement also supports that Yb 2 Ti 2 O 7 is a canted two-in-two-out ferromagnet with ordered moment of 0.90(3)μ B and a canting angle of 8 (6) • .…”

Magnon interactions in the frustrated pyrochlore ferromagnet Yb2Ti2O7

“…5(b). The classical transition field in this case, |B| ∼ 0.46 T, is lower than the |B| ∼ 0.65 T that has been recently observed experimen- tally [47]. Both theoretically and experimentally this is expected to be a first-order transition, with the gap remaining open across the transition.…”

“…We now turn to results for the third high symmetry field direction [111], which has been of interest recently [47]. Here we find considerable departures from LSWT even at |B| = 3 T [see Fig.…”

Role of defects in determining the magnetic ground state of ytterbium titanate

“…We find that oxygen vacancies stabilise the spin liquid phase and the stuffing of Ti sites by Yb suppresses it. Samples in which the oxygen vacancies have been eliminated by annealing in oxygen exhibit a transition to a ferromagnetic phase, and this is the true magnetic ground state.Yb2Ti2O7 has attracted intense experimental and theoretical interest as a model geometrically frustrated magnet with large quantum fluctuations [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . The crystalline electric field gives a Kramers doublet ground state well separated from the excited states 4 , and symmetry considerations lead to an effective spin ½ Hamiltonian with four exchange constants 5 .…”