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Abstract:

We present the results of x-ray scattering and muon-spin relaxation ([Formula: see text]SR) measurements on the iron-pnictide compound FeCrAs. Polarized non-resonant magnetic x-ray scattering results reveal the 120° periodicity expected from the suggested three-fold symmetric, non-collinear antiferromagnetic structure. [Formula: see text]SR measurements indicate a magnetically ordered phase throughout the bulk of the material below [Formula: see text] K. There are signs of fluctuating magnetism in a narrow range of temperatures above [Formula: see text] involving low-energy excitations, while at temperatures well below [Formula: see text] behaviour characteristic of freezing of dynamics is observed, likely reflecting the effect of disorder in our polycrystalline sample. Using density functional theory we propose a distinct muon stopping site in this compound and assess the degree of distortion induced by the implanted muon.

Abstract:

The quasi-one-dimensional molecule-based Heisenberg antiferromagnet Cu(NO3)2(pyz)3 has an intrachain coupling J = 13.7(1) K () and exhibits a state of long-range magnetic order below TN = 0.105(1) K. The ratio of interchain to intrachain coupling is estimated to be |J'/J| = 3.3 × 10-3, demonstrating a high degree of isolation for the Cu chains.

Abstract:

Wepresent the results of muon-spin spectroscopy (μ+SR) measurements on the molecular spin ladder system (Hpip)2CuBr4(1−x)Cl4x, [Hpip = (C5H12N)]. Using transverse field μ+SR we are able to identify characteristic behaviour in each of the regions of the phase diagram of the x = 0 strong-rung spin ladder system (Hpip)2CuBr4. Comparison of our results to those of the dimer-based molecular magnet Cu(pyz)(gly)(ClO4) shows several common features.Welocate the crossovers in partially disordered (Hpip)2CuBr4(1−x)Cl4x (x = 0.05), where a region of behaviour intermediate between quantum disordered and Luttinger liquid-like is identified. Our interpretation of the results incorporates an analysis of the probable muon stopping states in (Hpip)2CuBr4 based on density functional calculations and suggests how the muon plus its local distortion can lead to a local probe unit with good sensitivity to the magnetic state. Using longitudinal field μ+SR we compare the dynamic response of the x = 1 strong-rung material (Hpip)2CuCl4 to that of the strong-leg material (C7H10N)2CuBr4 (known as DIMPY) and demonstrate that our results are in agreement with predictions based on interacting fermionic quasiparticle excitations in these materials.