Crystal and magnetic structures in the Nd1-xSrxFeO3 (0.1 ≦ x ≦ 0.9) solid solutions

H. Nakatsugawa1, Y. Kamatani1, C. H. Hervoches2

1Yokohama National University, Japan, 2Nuclear Physics Institute, Rež, Czech Republic

 

Rare-earth orthoferrites RFeO3 (R=La,Nd,Dy,…) are of particular interest due to their potential multiferroicity, magnetoelectric effects, and other functional properties.

In this study, the Nd1-xSrxFeO3 series (0.1 ≤ x ≤ 0.9) have been prepared. Magnetization measurements from 5K to 700K show weak antiferromagnetic behaviour and paramagnetism following the typical Curie-Weiss law above 600K.

 

To clarify the correlation between the crystal structure and magnetic structure of Nd1-xSrxFeO3 (0.1 ≤ x ≤ 0.9), powder neutron diffraction (PND) data of the Nd1-xSrxFeO3 (0.1 ≤ x ≤ 0.9) samples were collected at 15K, 298K, and 500K with the medium resolution neutron powder diffractometer (MEREDIT), part of the CANAM infrastructure, at the Nuclear Physics Institute, Czech Republic. All Rietveld refinements were carried out using the GSAS-Ⅱ suite of programs [1].

It is confirmed that the FeO6 octahedron distortion is relaxed as x increases and approaches the crystal structure of the pseudo-cubic.  Fig 1 shows the evolution of Fe-O-Fe angles with x in Nd1-xSrxFeO3 (0.1 ≤ x ≤ 0.9).

At room temperature, the materials present antiferromagnetic order, with magnetic moment of Fe decreasing from ~ 3.2 µB for x = 0.1 to ~1.0 µB for x = 0.6 and magnetic spins oriented in the a- or c-axis (BNS Magnetic Space Group: P21’/m’, Pn'ma', or Pnma).

At 15K, in the range x = 0.1 – 0.4, the magnetic spins order in the b-axis direction (BNS Magnetic Space Group: P21’/m’ or Pn'ma'); A more complex magnetic structure is observed for x ≥ 0.5.

 

The magnetic structures for Nd0.9Sr0.1FeO3 at RT and 10K are shown in fig 2. Crystal and magnetic structures were drawn using VESTA [2].

RT

15K

 

Figure 1. Evolution of Fe-O-Fe angles vs x.

 
Figure 2. Magnetic structure of Nd0.9Sr0.1FeO3 (x = 0.1) at room temperature and 15K.

 

[1] B.H. Toby and R.B.Von Dreele, J. Appl. Cryst. 46, 544-549 (2013).

[2] K.Momma and F.Izumi, J.Appl.Crystallogr. 41, 653-658 (2008).

Keywords: Perovskites; magnetic materials; neutron diffraction

 

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