LaMn 3 Rh 4 O 12 : An Antiferromagnetic Quadruple Perovskite Synthesized at High Pressure Meixia Wu, † Corey E. Frank, ‡ Yifeng Han, † Mark Croft, § David Walker, ∥ Martha Greenblatt,* ,‡ and Man-Rong Li* ,† † Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. China ‡ Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, New Jersey 08854, United States § Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, United States ∥ Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, New York 10964, United States ABSTRACT: A quadruple perovskite LaMn 3 Rh 4 O 12 with A′ = Mn and B =4d transition metal was synthesized at high pressure (8 GPa) and temperature (1423 K) for the first time. Room temperature powder X-ray diffraction indicates that LaMn 3 Rh 4 O 12 forms in cubic symmetry (Im3̅ , a = 7.4997(1) Å). X-ray absorption near-edge spectroscopy shows predominantly Mn 3+ and Rh 3+ oxidation states. An antiferromagnetic transition at T N ∼ 41 K is corroborated by specific heat measurements. The resistivity measurements indicate a three-dimensional Mott variable-range hopping conduction mechanism between 300 and 160 K. ■ INTRODUCTION Transition-metal (TM) oxides with perovskite and related structures have been extensively studied due to their diverse and potentially useful physical properties for technological applications. 1−4 Simple ABO 3 perovskites can form A-site- ordered quadruple perovskites AA′ 3 B 4 O 12 , where typically 3/4 of the A-site ions (A′) are occupied by TMs, which generally are Jahn−Teller active cations, such as Co 2+ (low spin (LS) d 7 ), Cu 2+ , and Mn 3+ (high spin (HS) d 4 ) ions, or a square- planar d 8 ion like Pd 2+ , 5−7 while 1/4 of the A sites are generally occupied by moderately sized (usually between Cu 2+ and Sr 2+ as in CuCu 3 V 4 O 12 and SrCu 3 Fe 4 O 12 ) 4,8 mono- to trivalent cations such as alkali, alkali earth, rare earth metals, or Pb 2+ and Bi 3+ . The B-site ions are usually TMs. 6,9 The chemical and physical properties of quadruple perovskites are dominated by the interactions within and/or between the A/A′ and B sublattices, and also subtly correlated by the cation electronic configuration. For a given A- and B-site cation, small differences of electron configuration of the square-planar A′ and/or octahedral B cation can effect dramatic modification of the physical properties. For instance, LaMn 3 Cr 4 O 12 10 and BiMn 3 Mn 4 O 12 11 are antiferromagnets with two unique magnetic ordering temperatures, which are due to the A′-site and B-site ordering, respectively. Multiferroic properties were reported in cubic (Im3̅ ) LaMn 3 Cr 4 O 12 , 12 which cannot be understood by a conventional spin-driven microscopic mechanism (type-II multiferroics) and may be due to interactions between two magnetic sublattices. The Cu counterpart, LaCu 3 Cr 4 O 12 , is an unconventional metal and G-type antiferromagnet with Né el temperature (T N ) ∼ 225 K; 13,14 BiCu 3 Mn 4 O 12 15 is ferrimagnetic with a Curie temper- ature (T C ) of 350 K and is a low-resistive metal with low-field magnetoresistance effect up to −28% at 5 K. Recently, intense study has focused on quadruple perov- skites with 4d or 5d TMs at the B site with exotic physical properties. 7,16−35 The increased spatial extent of 4d and 5d TMs yields a weaker on-site Coulomb interaction and a higher Received: May 15, 2019 Published: July 25, 2019 Article pubs.acs.org/IC Cite This: Inorg. Chem. 2019, 58, 10280-10286 © 2019 American Chemical Society 10280 DOI: 10.1021/acs.inorgchem.9b01425 Inorg. Chem. 2019, 58, 10280−10286 Downloaded via SUN YAT SEN (ZHONGSHAN) UNIV on August 6, 2019 at 01:13:52 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.