Publications by Andrew Princep

Crystal field states of Tb3+ in the pyrochlore spin liquid Tb2Ti2O7 from neutron spectroscopy

PHYSICAL REVIEW B 91 (2015) ARTN 224430

AJ Princep, HC Walker, DT Adroja, D Prabhakaran, AT Boothroyd

Sc2NiMnO6: A Double-Perovskite with a Magnetodielectric Response Driven by Multiple Magnetic Orders.

Inorganic chemistry 54 (2015) 8012-8021

W Yi, AJ Princep, Y Guo, RD Johnson, D Khalyavin, P Manuel, A Senyshyn, IA Presniakov, AV Sobolev, Y Matsushita, M Tanaka, AA Belik, AT Boothroyd

Perovskite materials provide a large variety of interesting physical properties and applications. Here, we report on unique properties of a fully ordered magnetodielectric double-perovskite, Sc2NiMnO6 (space group P21/n, a = 4.99860 Å, b = 5.35281 Å, c = 7.34496 Å, and β = 90.7915°), exhibiting sequential magnetic transitions at T1 = 35 K and T2 = 17 K. The transition at T1 corresponds to a single-k antiferromagnetic phase with propagation vector k1 = (1/2, 0, 1/2), while the second transition at T2 corresponds to a 2-k magnetic structure with propagation vectors k1 = (1/2, 0, 1/2) and k2 = (0, 1/2, 1/2). Symmetry analysis suggests that the two ordering wave vectors are independent, and calculations imply that k1 is associated with the Mn sublattice and k2 with the Ni sublattice, suggesting that Mn-Ni coupling is very small or absent. A magnetodielectric anomaly at T2 likely arises from an antiferroelectric ordering that results from the exchange-striction between the two magnetic sublattices belonging to k1 and k2. The behavior of Sc2NiMnO6 demonstrates 3d double-perovskites with small A-site cations as a promising avenue in which to search for magnetoelectric materials.

Coupling of magnetic order to planar Bi electrons in the anisotropic Dirac metals AMnBi(2) (A = Sr, Ca)

PHYSICAL REVIEW B 90 (2014) ARTN 075120

YF Guo, AJ Princep, X Zhang, P Manuel, D Khalyavin, II Mazin, YG Shi, AT Boothroyd

Crystal-field states of Pr3+ in the candidate quantum spin ice Pr2Sn2O7

PHYSICAL REVIEW B 88 (2013) ARTN 104421

AJ Princep, D Prabhakaran, AT Boothroyd

A ferroelectric-like structural transition in a metal

Nature Materials 12 (2013) 1024-1027

Y Shi, Y Guo, X Wang, AJ Princep, D Khalyavin, P Manuel, Y Michiue, A Sato, K Tsuda, S Yu, M Arai, Y Shirako, M Akaogi, N Wang, K Yamaura, AT Boothroyd

Metals cannot exhibit ferroelectricity because static internal electric fields are screened by conduction electrons, but in 1965, Anderson and Blount predicted the possibility of a ferroelectric metal, in which a ferroelectric-like structural transition occurs in the metallic state. Up to now, no clear example of such a material has been identified. Here we report on a centrosymmetric () to non-centrosymmetric (R3c) transition in metallic LiOsO 3 that is structurally equivalent to the ferroelectric transition of LiNbO 3 (ref.). The transition involves a continuous shift in the mean position of Li + ions on cooling below 140 K. Its discovery realizes the scenario described in ref., and establishes a new class of materials whose properties may differ from those of normal metals. © 2013 Macmillan Publishers Limited. All rights reserved.

High-order Ho multipoles in HoB2C2 observed with soft resonant x-ray diffraction.

Journal of physics. Condensed matter : an Institute of Physics journal 24 (2012) 075602-

AJ Princep, AM Mulders, E Schierle, E Weschke, J Hester, WD Hutchison, Y Tanaka, N Terada, Y Narumi, T Nakamura

Soft resonant x-ray Bragg diffraction (SRXD) at the Ho M4,5 edges has been used to study Ho 4f multipoles in the combined magnetic and orbitally ordered phase of HoB2C2. A full description of the energy dependence for both σ and π incident x-rays at two different azimuthal angles, as well as the ratio I(σ)/I(π) as a function of azimuthal angle for a selection of energies, allows a determination of the higher order multipole moments of rank 1 (dipole) to 6 (hexacontatetrapole). The Ho 4f multipole moments have been estimated, indicating a dominant hexadecapole (rank 4) order with an almost negligible influence from either the dipole or the octupole magnetic terms. The analysis incorporates both the intra-atomic magnetic and quadrupolar interactions between the 3d core and 4f valence shells as well as the interference of contributions to the scattering that behave differently under time reversal. Comparison of SRXD, neutron diffraction and non-resonant x-ray diffraction shows that the magnetic and quadrupolar order parameters are distinct. The (00½) component of the magnetic order exhibits a Brillouin type increase below the orbital ordering temperature T(Q), while the quadrupolar order increases more sharply. We conclude that the quadrupolar interaction is strong, but quadrupolar order only occurs when the magnetic order gives rise to a quasi-doublet ground state, which results in a lock-in of the orbitals at T(Q).

REXS contribution to electronic ordering investigation in solids


TAW Beale, G Beutier, SR Bland, A Bombardi, L Bouchenoire, O Bunau, S Di Matteo, J Fernandez-Rodriguez, JE Hamann-Borrero, J Herrero-Martin, VLR Jacques, RD Johnson, A Juhin, T Matsumura, C Mazzoli, AM Mulders, H Nakao, J Okamoto, S Partzsch, AJ Princep, V Scagnoli, J Strempfer, C Vecchini, Y Wakabayashi, HC Walker, D Wermeille, Y Yamasaki

Triakontadipole and high-order dysprosium multipoles in the antiferromagnetic phase of DyB2C2.

Journal of physics. Condensed matter : an Institute of Physics journal 23 (2011) 266002-

AJ Princep, AM Mulders, U Staub, V Scagnoli, T Nakamura, A Kikkawa, SW Lovesey, E Balcar

Resonant soft x-ray Bragg diffraction at the Dy M(4,5) edges has been used to study Dy multipoles in the combined magnetic and orbitally ordered phase of DyB(2)C(2). The analysis incorporates both the intra-atomic magnetic and quadrupolar interactions between the 3d core and 4f valence shells. Additionally, we introduce to the formalism the interference of magnetic and nonmagnetic oscillators. This allows a determination of the higher-order multipole moments of rank 1 (dipole) to 6 (hexacontatetrapole). The strength of the Dy 4f multipole moments have been estimated as being up to 80% of the quadrupolar moment.

Circularly polarized soft x-ray diffraction study of helical magnetism in hexaferrite

PHYSICAL REVIEW B 81 (2010) ARTN 092405

AM Mulders, SM Lawrence, AJ Princep, U Staub, Y Bodenthin, M Garcia-Fernandez, M Garganourakis, J Hester, R Macquart, CD Ling