Crystal structure and magnetism in
Nd1-xSrxFeO3 (0.1 ≦ x ≦ 0.9)
H.Nakatsugawa1, Y.Kamatani1, C.H.Hervoches2
1Yokohama National University, Japan, 2Nuclear Physics Institute, Rež, Czech Republic

Neutron diffraction

Introduction, the samples
Rare-earth orthoferrites RFeO3 (R = La, Nd, Dy,…) are ofparticular interest due to their potential multiferroicity,magnetoelectric effects, and other functional properties.
In this study, several samples in the Nd1-xSrxFeO3 series(0.1 ≤ x ≤ 0.9) have been prepared, x-ray diffraction
confirmed the obtention of single phase with a typical ABO3
perovskite structure.
Magnetization
measurements from 5K
to 700K show weak
antiferromagnetic
behavior andparamagnetism
following the typicalCurie-Weiss law above
600K.

Powder neutron diffraction (λ=1.875 Å from a Si(311) monochromator) measurements were
performed for all Nd1-xSrxFeO3 (0.1 ≤ x ≤ 0.9) samples at room temperature.

Results confirmed that the FeO6 octahedron distortion is relaxed as x increases and approaches
the crystal structure of the pseudo-cubic.
Neutron diffraction for all samples could be refined in orthorhombic space group Pnma but, for0.1 ≦ x ≦ 0.2, the quality is improved with space group P21/m, as seen with the fitting of 202 (and20-2) reflections.
The following phase sequence is proposed:• 0.1 ≦ x ≦ 0.2 monoclinic P21/m• 0.3 ≦ x ≦ 0.9 orthorhombic Pnma

Pnma: 202 and 040

P21/m: 20-2, 202, 040

Crystal and magnetic structure change with x
Inverse magnetic susceptibility vs T
for Nd1-xSrxFeO3 (0.1 ≤ x ≤ 0.9)

In all samples, it is expected that Fe3+ is in low spin (LS) Fe3+(t2g5); s = 0.5 or intermediate spin (IS) Fe3+ (t2g4eg1); s = 1.5
and Fe4+ is in a low spin state (LS) Fe4+ (t2g4); s = 1.0.
Thus, assuming that the mixed valence state of Fe3+ and Fe4+ is(LS Fe3+y IS Fe3+1-y)1-x LS Fe4+x (0.1 ≤ x ≤ 0.9), the ratio of Fe4+
increases and that of Fe3+ decreases with increasing x.
In particular, the ratio of IS Fe3+, which accounts for thelargest proportion at x = 0.1 and 0.2, gradually decreases withincreasing x. This decrease in the ratio of IS Fe3+ to theincrease in x is expected to show a large correlation with therelaxation of the FeO6 octahedron distortion.

Lattice parameters

Fe-O-Fe angle

x = 0.1, P21/m, a = 5.567, b = 7.762, c = 5.465, β = 90.16o,magnetization vs x
magnetic SG at RT: P21/m, Mz = 3.4, at 10K: P21’/m’, My = 3.7

The instrument: MEREDIT(MEdium REsolution neutron powder
DIffracTometer)x = 0.5, Pnma, a = 5.456, b = 7.708, c = 5.489,

magnetic SG at RT: Pnma, Mx = 1.5

Layout of the instrument

Drawing of the crystal structure showing tilting of the FeO6
octahedron: in the (101) plane and about the b-axis,

PND of Nd0.1Sr0.9FeO3(x = 0.9) at RT

Sample environment• Variable temperature between 10 and 1300K with close
cycle cryostat and vacuum or light furnace.
• Carousel for automatic sample exchange at RT.
• Euler goniometer for texture measurements.
• Deformation rig for mechanical testing.

Magnetic structure

Conclusions:PND data of the Nd1-xSrxFeO3 samples were collected at RT for the whole series (0.1 ≤ x ≤ 0.9).
• The samples present antiferromagnetic ordering• At room temperature, the magnetic spins order in the shorter axis, i.e.:• for 0.1 ≤ x ≤ 0.3, the magnetic spins order in the c-axis direction (SG P21/m or Pn’ma’)• for 0.4 ≤ x ≤ 0.6, the magnetic spins order in the a-axis direction (SG Pnma)• At 10K, for Nd0.9Sr0.1FeO3 (x = 0.1), the magnetic spins order in the b-axis direction (SG : P21’/m’)

Users open access portal: http://canam.ujf.cas.czContact: hervoches@ujf.cas.cz

Acknowledgements: CANAM (MŠMT project No. LM2011019), and the infrastructure Reactors LVR-15 and LR-0 (MŠMTproject No. LM2018120) supported by the Ministry of Education, Youth and Sports of the Czech Republic.