Nanosized helical magnetic domains in strongly frustrated Fe3PO4O3

Article

关键词: DYNAMICS;    SKYRMION;    MAGNETOSTRICTION;    PHASE;   

DOI  :  10.1103/PhysRevB.92.134419

来源: SCIE

【 摘 要 】

Fe3PO4O3 forms a noncentrosymmetric lattice structure (space group R3m) comprising triangular motifs of Fe3+ coupled by strong antiferromagnetic interactions (vertical bar circle dot(CW)vertical bar > 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 similar to 86 angstrom. The magnetic structure consists of an unusual needlelike correlation volume that extends past 900 angstrom along the hexagonal c axis but is limited to similar to 70 angstrom in the ab 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 TN, as revealed by high-resolution synchrotron x-ray diffraction. The previously reported reduced moment of the Fe3+ ions (S = 5/2), mu similar to 4.2 mu(B), is confirmed here through magnetization studies of a magnetically diluted solid solution series of compounds, Fe(3-x)GaxPO4O3, and is consistent with the refined magnetic moment from neutron diffraction 4.14(2) mu(B). We attribute the reduced moment to a modified spin density distribution arising from ligand charge transfer in this insulating oxide.

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