Neutron powder diffraction study of the magnetic and crystal structures of SrFe{sub 2}(PO{sub 4}){sub 2}

Journal Article · Mon Sep 15 00:00:00 EDT 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.05.031· OSTI ID:21128445

Huang, Qingzhen ^[1]; Takayama-Muromachi, Eiji ^[2]; Lynn, Jeffrey W ^[1]

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1. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)
2. International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

The crystal and magnetic structures of SrFe{sup 2+}{sub 2}(PO{sub 4}){sub 2} have been determined by neutron powder diffraction data at low temperatures (space group P2{sub 1}/c (no. 14); Z=4; a=9.35417(13) A, b=6.83808(10) A, c=10.51899(15) A, and {beta}=109.5147(7){sup o} at 15 K). Two magnetic phase transitions were found at T{sub 1}=7.4 K (first-order phase transition) and T{sub 2}=11.4 K (second-order phase transition). The transition at T{sub 2} was hardly detectable by dc and ac magnetization measurements, and a small anomaly was observed by specific heat measurements. At T{sub 1}, strong anomalies were found by dc and ac magnetization and specific heat. The structure of SrFe{sub 2}(PO{sub 4}){sub 2} consists of linear four-spin cluster units, Fe2-Fe1-Fe1-Fe2. Below T{sub 1}, the propagation vector of the magnetic structure is k=[0,0,0]. The magnetic moments of the inner Fe1-Fe1 atoms of the four-spin cluster unit are ferromagnetically coupled. The magnetic moment of the outer Fe2 atom is also ferromagnetically coupled with that of the Fe1 atom but with spin canting. The four-spin cluster units form ferromagnetic layers parallel to the [-101] plane, while these layers are stacked antiferromagnetically in the [-101] direction. Spin canting of the outer Fe2 atoms provides a weak ferromagnetic moment of about 1 {mu}{sub B} along the b-axis. The refined magnetic moments at 3.5 K are 4.09 {mu}{sub B} for Fe1 and 4.07 {mu}{sub B} for Fe2. Between T{sub 1} and T{sub 2}, a few weak magnetic reflections were observed probably due to incommensurate magnetic order. - Graphical abstract: Temperature dependence of the intensities of representative magnetic reflections (-101) and (-1,1/2 ,1/2 ) during cooling and heating in SrFe{sub 2}(PO{sub 4}){sub 2}.

• OSTI ID: 21128445
• Journal Information: Journal of Solid State Chemistry, Vol. 181, Issue 9; Other Information: DOI: 10.1016/j.jssc.2008.05.031; PII: S0022-4596(08)00271-5; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CRYSTALS
IRON PHOSPHATES
LAYERS
MAGNETIC MOMENTS
MAGNETIZATION
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
PHASE TRANSFORMATIONS
SPACE GROUPS
SPECIFIC HEAT
SPIN
STRONTIUM PHOSPHATES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K