Complex magnetic order in topochemically reduced Rh(I)/Rh(III) LaM0.5Rh0.5O2.25 (M = Co, Ni) phases

DOI: 10.1021/acs.inorgchem.2c02747

Authors: Zheying Xu (University of Oxford) , Pardeep K. Thakur (Diamond Light Source) , Tien-Lin Lee (Diamond Light Source) , Anna Regoutz (University College London) , Emmanuelle Suard (Institut Laue-Langevin) , Inés Puente-Orench (Institut Laue-Langevin) , Michael A. Hayward (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Inorganic Chemistry , VOL 2

State: Published (Approved)
Published: September 2022
Diamond Proposal Number(s): 29451

Abstract: Topochemical reduction of the cation-disordered perovskite oxides LaCo0.5Rh0.5O3 and LaNi0.5Rh0.5O3 with Zr yields the partially anion-vacancy ordered phases LaCo0.5Rh0.5O2.25 and LaNi0.5Rh0.5O2.25, respectively. Neutron diffraction and Hard X-ray photoelectron spectroscopy (HAXPES) measurements reveal that the anion-deficient phases contain Co1+/Ni1+ and a 1:1 mixture of Rh1+ and Rh3+ cations within a disordered array of apex-linked MO4 square-planar and MO5 square-based pyramidal coordination sites. Neutron diffraction data indicate that LaCo0.5Rh0.5O2.25 adopts a complex antiferromagnetic ground state, which is the sum of a C-type ordering (mM5 +) of the xy-components of the Co spins and a G-type ordering (mΓ1 +) of the z-components of the Co spins. On warming above 75 K, the magnitude of the mΓ1 + component declines, attaining a zero value by 125 K, with the magnitude of the mM5 + component remaining unchanged up to 175 K. This magnetic behavior is rationalized on the basis of the differing d-orbital fillings of the Co1+ cations in MO4 square-planar and MO5 square-based pyramidal coordination sites. LaNi0.5Rh0.5O2.25 shows no sign of long-range magnetic order at 2 K − behavior that can also be explained on the basis of the d-orbital occupation of the Ni1+ centers.

Subject Areas: Chemistry, Materials, Physics


Instruments: I09-Surface and Interface Structural Analysis , I11-High Resolution Powder Diffraction

Added On: 25/09/2022 08:17

Discipline Tags:

Physics Physical Chemistry Chemistry Magnetism Materials Science Inorganic Chemistry Perovskites Metallurgy

Technical Tags:

Diffraction Spectroscopy X-ray Powder Diffraction X-ray Photoelectron Spectroscopy (XPS) Hard X-ray Photoelectron Spectroscopy (HAXPES)