Title: Nanosized helical magnetic domains in strongly frustrated ${\mathrm{Fe}}_3{\mathrm{PO}}_4{\mathrm{O}}_3$

Abstract

Fe₃PO₄O₃ forms a noncentrosymmetric lattice structure (space group R3m) comprising triangular motifs of Fe³⁺ coupled by strong antiferromagnetic interactions ( | Θ_CW | > 900 K). Neutron diffraction from polycrystalline samples shows that strong frustration eventually gives way to an ordered helical incommensurate structure below T_N =163 K, with the helical axis in the hexagonal ab plane and a modulation length to ~86 Å. The magnetic structure consists of an unusual needlelike correlation volume that extends past 900 Å along the hexagonal c axis but is limited to ~70 Å in the a b plane, despite the three-dimensional nature of the magnetic sublattice topology. The small in-plane correlation length, which persists to at least T = T_N/40 , indicates a robust blocking of long-range order of the helical magnetic structure, and therefore stable domain walls, or other defect spin textures, must be abundant in Fe₃PO₄O₃. Temperature-dependent neutron powder diffraction reveals small negative thermal expansion below T_N. No change in lattice symmetry is observed on cooling through T_N, as revealed by high-resolution synchrotron x-ray diffraction. The previously reported reduced moment of the Fe³⁺ ions (S = 5/2), μ ~ 4.2 μ_B, is confirmed here through magnetization studies of a magnetically dilutedmore » solid solution series of compounds, Fe_(3–x)Ga_xPO₄O₃, and is consistent with the refined magnetic moment from neutron diffraction 4.14(2) μ_B. Here, we attribute the reduced moment to a modified spin density distribution arising from ligand charge transfer in this insulating oxide.« less

Authors:

Ross, K. A. ^[1]; Bordelon, M. M. ^[1]; Terho, G. ^[1]; Neilson, J. R. ^[1]

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+ Show Author Affiliations

1. Colorado State Univ., Fort Collins, CO (United States)

Publication Date:

Mon Oct 26 00:00:00 EDT 2015

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1322370

Alternate Identifier(s):

OSTI ID: 1224362

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. B, Condensed Matter and Materials Physics

Additional Journal Information:

Journal Volume: 92; Journal Issue: 13; Journal ID: ISSN 1098-0121

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

ENGLISH

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY