Citation for published item:porondD pFF nd vngD pF nd w¤ ollerD tFF nd vnsterD F nd foothroydD eFF nd rttD pFvF nd qilinD FF nd rhkrnD hF nd flundellD FtF @PHISA 9enisotropi lol modi(tion of rystl (eld levels in rEsed pyrohlores X muonEindued e'et modeled using density funtionl theoryF9D hysil review lettersFD IIR @IAF HIUTHPF Further information on publisher's website: eprinted with permission from the emerin hysil oietyX porondD pFFD vngD pFD w¤ ollerD tFFD vnsterD FD foothroydD eFFD rttD pFvFD qilinD FFD rhkrnD hF nd flundellD FtF @PHISA 9enisotropi lol modi(tion of rystl (eld levels in rEsed pyrohlores X muonEindued e'et modeled using density funtionl theoryF9D hysil review lettersFD IIR @IAF HIUTHPF PHIS y the emerin hysil oietyF eders my viewD rowseD ndGor downlod mteril for temporry opying purposes onlyD provided these uses re for nonommeril personl purposesF ixept s provided y lwD this mteril my not e further reproduedD distriutedD trnsmittedD modi(edD dptedD performedD displyedD pulishedD or sold in whole or prtD without prior written permission from the emerin hysil oietyF Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

The low-temperature fluorination of the n = 2 Ruddlesden-Popper phase La2SrCr2O7 yields La2SrCr2O7F2 via a topochemical fluorine insertion reaction. The structure-conserving nature of the fluorination reaction means that the chromium centers of the initial oxide phase retain an octahedral coordination environment in the fluorinated product, resulting in a material containing an extended array of apex-linked Cr(4+)O6 units. Typically materials containing networks of octahedrally coordinated Cr(4+) centers can only be prepared at high pressure; thus, the preparation of La2SrCr2O7F2 demonstrates that low-temperature topochemical reactions offer an alternative synthesis route to materials of this type. Neutron diffraction, magnetization, and μ(+)SR data indicate that La2SrCr2O7F2 undergoes a transition to an antiferromagnetic state below TN ≈ 140 K. The structure-property relations of this phase and other Cr(4+) oxide phases are discussed.

We report magnetic, transport, neutron diffraction, and muon spin rotation data showing that Pb 2 CoOsO 6 , a metallic double-perovskite with a centrosymmetric space group at room temperature exhibits a continuous second-order phase transition at 45 K to a magnetically ordered state with a noncentrosymmetric space group. The absence of inversion symmetry is very uncommon in metals, particularly metallic oxides. In contrast to the recently reported ferroelectriclike structural transition in LiOsO 3 , the phase transition in Pb 2 CoOsO 6 is driven by a long-range collinear antiferromagnetic order, with propagation vector k = ( 1 2 , 0, 1 2 ), which relieves the frustration associated with the symmetry of the magnetic exchanges. This magnetically driven loss of inversion symmetry represents another frontier in the search for novel metallic behavior.

Muon spin rotation measurements have been performed on a powder sample of α-RuCl3, a layered material which previously has been proposed to be a quantum magnet on a honeycomb lattice close to a quantum spin liquid ground state. Our data reveal two distinct phase transitions at 11 K and 14 K which we interpret as originating from the onset of three-dimensional order and in-plane magnetic order, respectively. We identify, with the help of density functional theory calculations, likely muon stopping sites and combine these with dipolar field calculations to show that the two measured muon rotation frequencies are consistent with two inequivalent muon sites within a zig-zag antiferromagnetic structure proposed previously. PACS numbers: 76.75.+i, 71.15.Mb, 61.05.cp Solid-state systems with architectures that contain triangles or tetrahedra offer the possibility of realizing novel magnetically frustrated states, such as quantum spin liquids [1] or exotic topological phases [2]. One such candidate system for frustrated magnetism is α-RuCl 3 , which adopts the honeycomb structure. It is thought to be a spin-orbit assisted Mott insulator [3, 4], in which both the near two-dimensionality of the separate honeycomb layers and bond-dependent interactions, which may embody Kitaev physics, are proposed to be major ingredients [5]. Unconventional excitations observed via Raman [6] and inelastic neutron scattering [7] have been presented as evidence that α-RuCl 3 may be close to a quantum spin liquid ground state. Various magnetic transitions have been reported in α-RuCl 3 with early studies pointing towards an antiferromagnetic transition with numerous reported temperatures of 13 K [8], 15.6 K [9] or even 30 K [10], while later investigations proposed a potential second transition around 8 K [11][12][13] thought to originate from low-moment magnetism. Recent neutron powder diffraction provided evidence for a single transition to a zig-zag antiferromagnetic state with 2-layer stacking at T N = 13 K [14], though a later single crystal neutron study has proposed a single transition at 8 K to a 3-layer stacking magnetic order in pristine single crystals and a change of T c to 14 K upon mechanical deformation of the crystals [15]. These differences in observed properties could be due to the propensity of this compound to exhibit stacking faults between the weakly coupled honeycomb layers [14].Positive muons as local magnetic probes present an ideal tool for detecting magnetic order and characterizing magnetic behavior, and have been extensively utilized in muon-spin rotation or relaxation (µ Polycrystalline samples of α-RuCl 3 were synthesized by vacuum sublimation from commercial RuCl 3 powder (Sigma Aldrich), which was sealed in a quartz ampoule (p ≈ 10 −5 mbar) and placed in a three-zone furnace with a hot and cold end of 650 • C and 450• C, respectively. Those temperatures were chosen in order to obtain phase-pure α-RuCl 3 (the β-polytype transforms irreversibly into the α-phase above 395• C) and to keep the Cl 2 gas press...

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