https://doi.org/10.1140/epjb/e2009-00019-5
Crystal and magnetic structure of single-crystal La1-xSrxMnO3 (x ≈ 1/8)
Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
Corresponding author: a h.f.li@hotmail.com
Received:
14
July
2008
Revised:
10
November
2008
Published online:
24
January
2009
A neutron powder diffraction (NPD) study on the crystal and magnetic
structure of a crushed La1-xSrxMnO3 (x ≈ 1/8) single
crystal has been performed. The sample belongs to orthorhombic (Pnma, O) above
the Jahn-Teller (JT) transition temperature (TJT) and monoclinic
(P121/c1, M′) in the JT regime. We have also refined the NPD data below
the charge/orbital ordering (CO/OO) temperature (TCO/OO) with a
monoclinic (P121/c1, M′′) model because the experimental resolution was
insufficient to clearly identify a triclinic structure. The
refined lattice parameters show an obvious breathing-mode distortion between
TCO/OO and TJT, accompanied by a large deviation of the monoclinic
angle β from 90°, signifying a very strong cooperative JT
distortion. A ferromagnetic (FM) moment of 3.43(5) μB/Mn besides an
A-type antiferromagnetic (A-AFM) moment of 0.54(2) μB/Mn is directed
mainly along the b axis in P121/c1 symmetry at 5 K. With increasing
temperature, the A-AFM domains transform into FM ones above ~100 K and
the FM spin orientation turns from the b to the c axis in crystallographic
b-c plane below Tc = 187(1) K. The magnetization measurements show typical
anomalies around TCO/OO and TJT. The measured saturation moment of
3.9(1) μB/Mn at 70 kOe and 5 K is well consistent with the sum 3.97(5) μB/Mn
of the refined FM and A-AFM moments at 5 K, implying the A-AFM spins are
aligned in field direction at 70 kOe. The applied magnetic field can affect
the paramagnetic insulating (PMI) state in the range of magnetic polarons.
Based on the size of JT distortion and the bond-valence sums (BVS's), the
CO/OO phenomenon is being discussed.
PACS: 61.05.F- – Neutron diffraction and scattering / 61.50.Ks – Crystallographic aspects of phase transformations; pressure effects / 76.50.+g – Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance / 67.80.dk – Magnetic properties, phases, and NMR / 61.43.Gt – Powders, porous materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009