The Highly Frustrated 5d Double Perovskite Doppelgängers, SrLaMgReO and SrLaLiOsO. A Comparison including Isostructural LaLiReO.

The synthesis and characterization of the double perovskite SrLaLiOsO is presented. It is isostructural (2/) and isoelectronic (5d) with SrLaMgReO, which has been reported previously. The cell volumes are the same to within 1.

Spin-Density Wave as a Superposition of Two Magnetic States of Opposite Chirality and Its Implications.

A magnetic solid with weak spin frustration tends to adopt a noncollinear magnetic structure such as a cycloidal structure below a certain temperature and a spin-density wave (SDW) slightly above this temperature. The causes for these observations were explored by studying the magnetic structure of BaYFeO, which undergoes a SDW and a cycloidal phase transition below 48 and 36 K, respectively, in terms of the density functional theory calculations. We show that a SDW structure arises from a superposition of two magnetic states of opposite chirality, an SDW state precedes a chiral magnetic state because of the lattice relaxation, and whether a SDW is transversal or longitudinal is governed by the magnetic anisotropy of magnetic ions.

Identifying the local structural units in LaBaMnO and BaYFeO through the neutron pair distribution function.

Neutron pair distribution function data are used to investigate the local structures of two oxygen deficient perovskites with simple cubic crystal structures. LaBaMnO is found to have alternating layers of MnO octahedra and MnO tetrahedra, making it similar to other members of the LaBaMnO series with smaller x values which have brownmillerite crystal structures. Our fitting results suggest that LaBaMnO is not locally similar to any one brownmillerite structure type but instead has a variety of intra-layer and inter-layer relationships.

Cubic Re (5d) Double Perovskites, BaMgReO, BaZnReO, and BaYReO: Magnetism, Heat Capacity, μSR, and Neutron Scattering Studies and Comparison with Theory.

Double perovskites (DP) of the general formula BaMReO, where M = Mg, Zn, and Y, all based on Re (5d, t), were synthesized and studied using magnetization, heat capacity, muon spin relaxation, and neutron-scattering techniques. All are cubic, Fm3̅m, at ambient temperature to within the resolution of the X-ray and neutron diffraction data, although the muon data suggest the possibility of a local distortion for M = Mg. The M = Mg DP is a ferromagnet, T = 18 K, with a saturation moment ∼0.

Synthesis, structure, and magnetic properties of novel B-site ordered double perovskites, SrLaMReO6 (M = Mg, Mn, Co and Ni).

Four new double perovskites, SrLaMReO(6) (M = Mg, Mn, Co, Ni) in which Re(5+) (5d(2)) is present, were prepared via conventional solid state reactions and characterized by X-ray and neutron powder diffraction, XANES, SQUID magnetometry, and muon spin relaxation (μSR). Synchrotron X-ray and neutron diffraction experiments confirmed that all compounds crystallize in the monoclinic P2(1)/n structure type, which consists of alternately corner-shared octahedra of MO(6) and ReO(6). Rietveld refinement results indicated anti-site mixing of less than 7% on the M/Re sites.

Partial spin ordering and complex magnetic structure in BaYFeO4: a neutron diffraction and high temperature susceptibility study.

The novel iron-based compound, BaYFeO4, crystallizes in the Pnma space group with two distinct Fe(3+) sites, that are alternately corner-shared [FeO5](7-) square pyramids and [FeO6](9-) octahedra, forming into [Fe4O18](24-) rings, which propagate as columns along the b-axis. A recent report shows two discernible antiferromagnetic (AFM) transitions at 36 and 48 K in the susceptibility, yet heat capacity measurements reveal no magnetic phase transitions at these temperatures. An upturn in the magnetic susceptibility measurements up to 400 K suggests the presence of short-range magnetic behavior at higher temperatures.

Magnetocaloric effect in AlFe2B2: toward magnetic refrigerants from earth-abundant elements.

AlFe2B2 was prepared by two alternative synthetic routes, arc melting and synthesis from Ga flux. In the layered crystal structure, infinite chains of B atoms are connected by Fe atoms into two-dimensional [Fe2B2] slabs that alternate with layers of Al atoms. As expected from the theoretical analysis of electronic band structure, the compound exhibits itinerant ferromagnetism, with the ordering temperature of 307 K.

Spin-glass behavior in LaFe(x)Co(2-x)P2 solid solutions: interplay between magnetic properties and crystal and electronic structures.

To explore the evolution of magnetic properties from ferromagnetic LaCo(2)P(2) to paramagnetic LaFe(2)P(2) (both of ThCr(2)Si(2) structure type) a series of mixed composition LaFe(x)Co(2-x)P(2) (x ≤ 0.5) has been comprehensively investigated by means of single-crystal and powder X-ray and neutron diffraction, magnetization and heat capacity measurements, Mössbauer spectroscopy, and electronic band structure calculations. The Curie temperature decreases from 132 K in LaCo(2)P(2) to 91 K in LaFe(0.

Synthesis of ThCr2Si2-type arsenides from Bi flux.

LaCo(2)As(2) can be synthesized as pure crystalline material by annealing a mixture of elements in Bi flux. The reaction, however, is accompanied by the incorporation of a small quantity of Bi into the structure and the formation of vacancies in the Co sublattice, which lead to substantial changes in structural and magnetic properties of the material.