Magnetic structure and crystal-field states of the pyrochlore antiferromagnetNd2Zr2O7

Abstract

We present synchrotron x-ray diffraction, neutron powder diffraction and time-of-flight inelastic neutron scattering measurements on the rare earth pyrochlore oxide Nd2Zr2O7 to study the ordered state magnetic structure and cystal field states. The structural characterization by high-resolution synchrotron x-ray diffraction confirms that the pyrochlore structure has no detectable O vacancies or Nd/Zr site mixing. The neutron diffraction reveals long range all-in/all-out antiferromagnetic order below TN ≈ 0.4 K with propagation vector k = (0 0 0) and an ordered moment of 1.26(2) µB/Nd at 0.1 K. The ordered moment is much smaller than the estimated moment of 2.65 µB/Nd for the local 111 Ising ground state of Nd 3+ (J = 9/2) suggesting that the ordering is partially suppressed by quantum fluctuations. The strong Ising anisotropy is further confirmed by the inelastic neutron scattering data which reveals a well-isolated dipolar-octupolar type Kramers doublet ground state. The crystal field level scheme and ground state wavefunction have been determined.

Intermultiplet transitions and magnetic long-range order in Sm-based pyrochlores

“…Neutron diffraction probes directly only dipolarordering, while octupolar interactions can be indirectly inferred from the magnetic excitations present in the material [31,33]. As the matrix elements of the octupolar tensor in 154 Sm 2 Ti 2 O 7 and 154 Sm 2 Sn 2 O 7 are significantly smaller that those in Nd 2 Zr 2 O 7 [31,34], possibly neutron scattering techniques are not, after all, ideal to check any of those in Sm-based pyrochlores. In this regard, more studies, especially measurements of dynamic susceptibility at low temperatures, would be indispensable.…”

A New Family of Disorder-Free Rare-Earth-Based Kagome Lattice Magnets: Structure and Magnetic Characterizations of RE3BWO9 (RE = Pr, Nd, Gd–Ho) Boratotungstates

“…This value is close to the half value of low temperature fitted moment as observed in other Nd 3+ based oxides. 28,29 Gd3BWO9. The χ(T) of Gd3BWO9 is shown in Figure 4c, no signature of magnetic order is seen down to 2 K. The high-temperature Curie-Weiss fitting of χ -1 (T) yields θCW = -3.64 K and µeff = 8.6 µB.…”

Upper branch magnetism in quantum magnets: Collapses of excited levels and emergent selection rules

“…The widely accepted standard approach is to understand the crystal field level and find the local ground states 9 . The local ground states can be usual Kramers doublets [10][11][12][13][14][15][16][17][18] , dipole-octupole doublets [19][20][21][22][23][24][25] , and non-Kramers doublets [26][27][28][29][30][31][32][33] , and these local ground states control the low-temperature magnetic properties of many rare-earth magnets. This standard approach has found a great success in the study of rareearth pyrochlore magnets such as Yb 2 Ti 2 O 7 10,15,34,35 and Er 2 Ti 2 O 7 [35][36][37][38][39] rare-earth triangular magnets such as YbMgGaO 4 13,40-53 , and rare-earth based double per-ovskites 54 62 may also be interpreted under this scheme.…”