Probing magnetic order and disorder in the one-dimensional molecular spin chains CuF₂(pyz) and [Ln(hfac)₃(boaDTDA)] _n (Ln  =  Sm, La) using implanted muons

Abstract

We present the results of muon-spin relaxation (µ + SR) measurements on antiferromagnetic and ferromagnetic spin chains. In antiferromagnetic CuF 2 (pyz) we identify a transition to long range magnetic order taking place at T N = 0.6(1) K, allowing us to estimate a ratio with the intrachain exchange of T N /|J| ≈ 0.1 and the ratio of interchain to intrachain exchange coupling as |J /J| ≈ 0.05. The ferromagnetic chain [Sm(hfac) 3 (boaDTDA)] n undergoes an ordering transition at T c = 2.8(1) K, seen via a broad freezing of dynamic fluctuations on the muon (microsecond) timescale and implying T c /|J| ≈ 0.6. The ordered radical moment continues to fluctuate on this timescale down to 0.3 K, while the Sm moments remain disordered. In contrast, the radical spins in [La(hfac) 3 (boaDTDA)] n remain magnetically disordered down to T = 0.1 K suggesting T c /|J| < 0.17. arXiv:1905.04913v1 [cond-mat.str-el]

Anomalous magnetic exchange in a dimerized quantum magnet composed of unlike spin species

“…For the reasons outlined above, significant exchange through a JT bond is very rare. However, a similar scenario has been encountered once before in the 2D AFM chain compounds CuX 2 (pyz); where X = Cl, Br, F [54][55][56]. In this case, however, magnetic exchange is mediated along Cu--X 2 --Cu bibridges, for which only one of the X--Cu--X bridges lies along the JT axial direction, while the other lies in the plane containing the d x 2 −y 2 magnetic orbital [56].…”

“…However, a similar scenario has been encountered once before in the 2D AFM chain compounds CuX 2 (pyz); where X = Cl, Br, F [54][55][56]. In this case, however, magnetic exchange is mediated along Cu--X 2 --Cu bibridges, for which only one of the X--Cu--X bridges lies along the JT axial direction, while the other lies in the plane containing the d x 2 −y 2 magnetic orbital [56]. This means that, in the present case, the manner in which the intradimer exchange is mediated through the O atom on the Cu(II) JT axis remains unusual [57].…”

Single-ion magnetism behaviors in lanthanide(iii) based coordination frameworks

“…67 Such a radical strategy can also be utilized to construct Ln( iii )-based chain structures, such as the ferromagnetic chain structure [Sm(hfac) 3 (boaDTDA)] n with the ordering transition at T c = 3 K, reported by Preuss and co-workers in 2016. 68,69 The dysprosium chain compound ( 6 ) is assembled by an azido-bridged (N 3 − ) radical ligand, which was reported by Tian and co-workers in 2021. Compound 6 shows slow magnetic relaxation under zero-field, 63 with an effective energy barrier of around 45.9 K and ferromagnetic coupling between the discrete Dy( iii ) ions (Fig.…”

Learning from Physics Experiments with Quantum Computers: Applications in Muon Spectroscopy

“…As described above, µ + SR experiments have been used to investigate a range of physical phenomena. For example, we can measure the temperature dependence of oscillations in the polarisation function (or the lack thereof) in order to investigate phase transitions in magnetic materials, such as low dimensional spin chains [19]. Other experiments have measured the polarisation function of muons in semiconductors, at a range of temperatures, in order to investigate the diffusion of muons within the sample.…”