Journal Article

FZJ-2015-03011

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Determination of the magnetic order and the crystal symmetry in the multiferroic ground state of Ba$_{2}$CoGe$_{2}$O$_{7}$

Hutanu, V. (Corresponding Author)FZJ* ; Sazonov, A.FZJ* ; Meven, M.FZJ* ; Murakawa, H. ; Tokura, Y. ; Bordács, S. ; Kézsmárki, I. ; Náfrádi, B.

2012
APS College Park, Md.

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Please use a persistent id in citations: http://hdl.handle.net/2128/8581  doi:10.1103/PhysRevB.86.104401

Abstract: Detailed structural investigation of Ba2CoGe2O7 was performed in its low-temperature multiferroic state combining neutron diffraction with magnetization measurements and the optical study of lattice vibrations on single crystals. The crystal structure above (10.4 K) and the crystal and magnetic structures below (2.2 K) the antiferromagnetic transition temperature of TN = 6.7 K were determined using neutron diffraction. The tetragonal space group (SG) P-421m, corresponding to the average structure at room temperature, was found to also describe the structure at low temperatures well. Neutron diffraction data and infrared phonon mode analysis imply no structural phase transition down to 2.2 K. Orthorhombic polar SG Cmm2 is proposed as a true crystal structure. Below TN, the spins of the Co2+ ions form a square-lattice Néel order within the (a,b) plane, while their alignment is ferromagnetic along the c axis. The magnitude of the ordered moment, fully lying within the (a,b) plane, is found to be 2.9(1) μB/Co2+ and the easy axis of the sublattice magnetizations corresponds to the [110] direction. A noncollinear spin structure due to small canting is allowed.

Keyword(s): Key Technologies (1st) ; Energy (1st) ; Information Technology and Functional Materials (1st) ; Condensed Matter Physics (2nd) ; Magnetism (2nd) ; Crystallography (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)
2. Streumethoden (JCNS-2)

Research Program(s):

1. 422 - Spin-based and quantum information (POF2-422) (POF2-422)
2. 424 - Exploratory materials and phenomena (POF2-424) (POF2-424)
3. 542 - Neutrons (POF2-542) (POF2-542)
4. 544 - In-house Research with PNI (POF2-544) (POF2-544)
5. 54G - JCNS (POF2-54G24) (POF2-54G24)

Experiment(s):

1. HEiDi: Single crystal diffractometer on hot source (SR9b)
2. POLI: Polarized hot neutron diffractometer (SR9a)

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Database coverage:
; ; ; Current Contents - Physical, Chemical and Earth Sciences ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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