Magnetic Phase Separation in the Oxypnictide Sr2Cr1.85 Mn1.15As2O2

The authors thank the U.K. Science and Technology Facilities Council (STFC) for provision of neutron beamtime at the ILL under the experiment code 5-31-2665. Data are available from ILL at DOI:10.5291/ILL-DATA.5-31-2665.Peer reviewedPublisher PD

Electronic Phase Separation in the Hexagonal Perovskite Ba3SrMo2O9

ACKNOWLEDGEMENTS We thank the Carnegie Trust for the Universities of Scotland for a PhD Scholarship for S.S. We acknowledge STFC-GB for provision of beamtime at the ILL. We also thank Dr. Mark Senn (University of Warwick) for useful discussions.Peer reviewedPostprin

The Electronic and Magnetic Properties of Cation Ordered Sr2Mn2.23Cr0.77As2O2

ACKNOWLEDGMENT This research is supported by the EPSRC (research grant EP/L002493/1). We also acknowledge the UK Science and Technology Facilities Council (STFC) for provision of beam time at the ILL.Peer reviewedPostprin

Anomalous evolution of the magnetocaloric effect in dilute triangular Ising antiferromagnets Tb1−xYx(HCO2)3Tb_{1-x}Y_{x}(HCO_{2})_{3}

We investigate the effects of diamagnetic doping in the solid-solution series $Tb_{1-x}Y_{x}(HCO_{2})_{3}$, in which the parent $Tb(HCO_{2})_{3}$ phase has previously been shown to host a combination of frustrated and quasi-1D physics, giving rise to a triangular Ising antiferromagnetic ground state that lacks long range 3D order. Heat capacity measurements show three key features: (i) a low temperature Schottky anomaly is observed, which is constant as a function of x; (ii) the transition temperature and associated entropy change are both surprisingly robust to diamagnetic doping; and (iii) an additional contribution at T < 0.4 K appears with increasing x. The origin of this unusual behaviour is rationalised in terms of the fragmentation of quasi-1D spin chains by the diamagnetic $Y^{3+}$ dopant. Magnetocaloric measurements show a nonlinear dependence on x. The mass-weighted magnetocaloric entropy decreases across the series from the promising values in $Tb(HCO_{2})_{3}$; however, the magnetocaloric entropy per magnetic $Tb^{3+}$ ion first decreases then increases with increasing x. Our results establish $Tb_{1-x}Y_{x}(HCO_{2})_{3}$ as a model system in which to explore the functional ramifications of dilution in a low-dimensional magnet.Comment: 11 pages and 5 figures excluding supplementary informatio

Localised spin dimers and structural distortions in the hexagonal perovskite Ba3CaMo2O9

Open Access under the ACS OA Agreement Acknowledgments JWe thank the Carnegie Trust for the Universities of Scotland for a PhD Scholarship for S.S. and the U.K. Science and Technology Facilities Council (STFC) for provision of neutron beamtime at the ILL under the experiment code 5-31-2703. Data are available from ILL at DOI: 10.5291/ILL-DATA.5-31-2703.Peer reviewedPublisher PD

Magnetocaloric Ln(HCO2_2)(C2_2O4_4) frameworks: Synthesis, Structure and Magnetic Properties

This study probes the structure and the magnetic properties of members of the Ln(HCO$_2$)(C$_2$O$_4$) (Ln = Sm$^{3+}$–Er$^{3+}$) family of coordination frameworks. These frameworks adopt Pnma orthorhombic symmetry with one-dimensional chains arranged on a distorted triangular lattice. The magnetic properties of the Gd–Ho members of this series indicate they remain paramagnetic down to 2 K, with Dy(HCO$_2$)(C$_2$O$_4$) magnetically ordering at 0.6 K. The magnetocaloric effect of Gd(HCO$_2$)(C$_2$O$_4$) is amongst the highest found in frameworks with a peak entropy change of 55.97 J kg$^{-1}$ K$^{-1}$ (218.42 mJ cm$^{-3}$ K$^{-1}$) for a 5–0 T field change at T$_{max}$ = 2 K, making this material a very good candidate for ultra-low temperature magnetic cooling. In contrast with related magnetocaloric materials lanthanides with high magnetocrystalline anisotropy do not generally improve the magnetocaloric performance of this family at higher temperatures and lower fields. Neutron diffraction experiments suggest that Tb(HCO$_2$)(C$_2$O$_4$) and Ho(HCO$_2$)(C$_2$O$_4$) lack significant local magnetic correlations, highlighting the key role these play in optimising the magnetocaloric performance in low fields in related phases; this emphasises the importance of designing materials with specific magnetic interactions to optimise magnetocaloric performance

In situ observation of the magnetocaloric effect through neutron diffraction in the Tb(DCO2)3Tb(DCO_2)_3 and TbODCO3TbODCO_3 frameworks

Probing the magnetic structure of magnetocaloric materials in applied fields, can reveal detailed insight into the mechanism of magnetic refrigeration thereby linking the magnetic states that form under applied magnetic fields to changes in magnetic entropy. This study probes the long range magnetic order in $Tb(DCO_2)_3$ and $TbODCO_3$ as a function of temperature and applied magnetic field, through neutron diffraction measurements. A triangular Ising antiferromagnetic phase is formed, in small applied magnetic fields in $Tb(DCO_2)_3$, a spin flip transition occurs to a simple ferromagnetic structure in higher applied fields. $TbODCO_3$ undergoes a phase transition, in applied fields, into two magnetic phases; namely a buckled chain ferromagnetic phase along the b-axis and a canted antiferromagnetic phase, with a ferromagnetic component along c-axis. Both of the states observed in $TbODCO_3$ are consistent with Ising-like anisotropy previously reported in $TbODCO_3$ and the coexistance of these is likely the result of applying a magnetic field to a powdered sample

Observation of an Exotic Insulator to Insulator Transition upon Electron Doping the Mott Insulator CeMnAsO

Acknowledgements This research was supported by EPSRC (Grant no. EP/L002493/1 (A.C.M.)), The Carnegie Trust for the Universities of Scotland (PhD scholarship for S.S. (S.S.)) and the ILL (PhD studentship for G.B.L. (A.C.M.)). By the membership of the UK's HEC Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202 (A.W.)), this work used the ARCHER2 UK National Supercomputing Service (http://www.archer2.ac.uk). We also acknowledge STFC-GB for provision of beamtime at the ILL.Peer reviewe