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We present the results of muon-spin relaxation measurements of spin excitations in the one-dimensional quantum Heisenberg antiferromagnet Cu(pyz)(NO$_{3}$)$_{2}$. Using density-functional theory we propose muon sites and assess the degree of perturbation the muon probe causes on the system. We identify a site involving the muon forming a hydroxyl-type bond with an oxygen on the nitrate group that is sensitive to the characteristic spin dynamics of the system. Our measurements of the spin dynamics show that in the temperature range $T_{mathrm{N}}<T<J$ (between the ordering temperature $T_{mathrm{N}}$ and the exchange energy scale $J$) the field-dependent muon spin relaxation is characteristic of diffusive transport of spin excitations over a wide range of applied fields. We also identify a possible crossover at higher applied fields in the muon probes response to the fluctuation spectrum, to a regime where the muon detects early-time transport with a ballistic character. This behavior is contrasted with that found for $T>J$ and that in the related two-dimensional system Cu(pyz)$_2$(ClO$_4$)$_{2}$.
We present the results of muon-spin relaxation ($mu^{+}$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 $T_{mathrm{N}} = 0.
The study of randomness in low-dimensional quantum antiferromagnets is at the forefront of research in the field of strongly correlated electron systems, yet there have been relatively few experimental model systems. Complementary neutron scattering
From experimental and theoretical analyses of magnetic and specific-heat properties, we present the complete magnetic phase diagram of the quasi-one-dimensional antiferromagnet Cu(N$_2$H$_5$)$_2$(SO$_4$)$_2$. On cooling and at zero magnetic field thi
We believe that a necessary first step in understanding the ground state properties of the spin-${scriptstylefrac{1}{2}}$ kagome Heisenberg antiferromagnet is a better understanding of this models very large number of low energy singlet states. A des
Chiral magnets with topologically nontrivial spin order such as Skyrmions have generated enormous interest in both fundamental and applied sciences. We report broadband microwave spectroscopy performed on the insulating chiral ferrimagnet Cu$_{2}$OSe