Electronic and magnetic properties of ${\mathrm{RuSr}}_2{\mathrm{GdCu}}_2{\mathrm{O}}_8$ have been investigated by electric resistivity, magnetization, and Cu-, Ru-NMR measurements. Magnetic order ${(T}_M=133\mathrm{}\hspace{0.5em}\mathrm{K})$ and superconductivity $\left[T_s\right(\mathrm{onset}\left)\sim 52\hspace{0.5em}\mathrm{K}\right]$ have been confirmed. We observed two kinds of Ru-NMR signals (the hyperfine fields of ${}^{101}\mathrm{Ru}$ are 590 kOe and 290 kOe), suggesting a charge segregation of ${\mathrm{Ru}}^{5+}\hspace{0.5em}\mathrm{}(S=3/2\mathrm{})\mathrm{}$ and ${\mathrm{Ru}}^{4+}\hspace{0.5em}\mathrm{}(S=1\mathrm{})\mathrm{}$ in the ${\mathrm{RuO}}_2$ layers. The hyperfine field at the Cu site is diminishingly small, indicating magnetic interactions between ${\mathrm{CuO}}_2$ and ${\mathrm{RuO}}_2$ layers are weak. Assuming that holes are inherently doped in the ${\mathrm{CuO}}_2$ layers from the $({\mathrm{Ru}}^{4+},$ ${\mathrm{Ru}}^{5+}){\mathrm{O}}_2$ layers, the high-$T_c$ superconductivity can occur under weak magnetic interactions between Ru and Cu spins in ${\mathrm{RuSr}}_2{\mathrm{GdCu}}_2{\mathrm{O}}_8.$

We present a combined study of zero-field ${}^{51}\mathrm{V}$ and ${}^{127}\mathrm{I}$ NMR at ambient pressure and specific heat and magnetization measurements under pressure up to 2.08 GPa on bulk single crystals of the van der Waals ferromagnet ${\mathrm{VI}}_3$. At ambient pressure, our results consistently demonstrate that ${\mathrm{VI}}_3$ undergoes a structural transition at $T_s\approx 78\mathrm{K}$, followed by two subsequent ferromagnetic transitions at $T_{\mathrm{FM}1}\approx 50\mathrm{K}$ and $T_{\mathrm{FM}2}\approx 36\mathrm{K}$ upon cooling. At lowest temperature $\left(T<T_{\mathrm{FM}2}\right)$, two magnetically ordered V sites exist, whereas only one magnetically ordered V site is observed for $T_{\mathrm{FM}1}<T<T_{\mathrm{FM}2}$. Whereas $T_{\mathrm{FM}1}$ is almost unaffected by external pressure, $T_{\mathrm{FM}2}$ is highly responsive to pressure and merges with the $T_{\mathrm{FM}1}$ line at $p\approx 0.6\mathrm{GPa}$. At even higher pressures $\left(p\approx 1.25\mathrm{GPa}\right)$, the $T_{\mathrm{FM}2}$ line merges with the structural transition at $T_s$ which becomes moderately suppressed with $p$ for $p<1.25\mathrm{GPa}$. Taken together, our data point toward a complex magnetic structure and an interesting interplay of magnetic and structural degrees of freedom in ${\mathrm{VI}}_3$.

A spin-triplet superconducting state mediated by ferromagnetic (FM) spin fluctuations has been suggested to occur in the newly discovered heavy-fermion superconductor ${\mathrm{UTe}}_2$. However, the recent neutron scattering measurements revealed the presence of antiferromagnetic (AFM) spin fluctuations in ${\mathrm{UTe}}_2$. Here, we report the ${}^{125}\mathrm{Te}$ nuclear magnetic resonance studies of a single-crystal ${\mathrm{UTe}}_2$, suggesting the coexistence of FM and AFM spin fluctuations in ${\mathrm{UTe}}_2$. Owing to the two different Te sites in the compound, we conclude that the FM spin fluctuations are dominant within ladders and the AFM spin fluctuations originate from the interladder magnetic coupling. Although AFM spin fluctuations exist in the system, the FM spin fluctuations in the ladders may play an important role in the appearance of the spin-triplet superconducting state of ${\mathrm{UTe}}_2$.

We report x-ray diffraction, magnetic susceptibility, heat capacity, ${}^1\mathrm{H}$ nuclear magnetic resonance (NMR), and muon spin relaxation $\left(\mu \mathrm{SR}\right)$ measurements, as well as density-functional band-structure calculations for the frustrated $S=3/2$ triangular lattice Heisenberg antiferromagnet (TLHAF) $\alpha \text{−}{\mathrm{HCrO}}_2$ (trigonal, space group: $R\overline{3}m$). This compound undergoes a clear magnetic transition at $T_{\mathrm{N}}\simeq 22.5$ K, as seen from the drop in the muon paramagnetic fraction and concurrent anomalies in the magnetic susceptibility and specific heat capacity. Local probes (NMR and $\mu \mathrm{SR}$) reveal a broad regime with slow fluctuations down to $0.7T_{\mathrm{N}}$, this temperature corresponding to the maximum in the $\mu \mathrm{SR}$ relaxation rate and in the NMR wipe-out. From the comparison with ${\mathrm{NaCrO}}_2$ and $\alpha \text{−}{\mathrm{KCrO}}_2$, the fluctuating regime and slow dynamics below $T_{\mathrm{N}}$ appear to be hallmarks of the TLHAF with $ABC$ stacking. We discuss the role of interlayer frustration, which may have impacted recent spin-liquid candidates with triangular geometry.

We report synthesis and magnetic properties of quasi-one-dimensional spin-$\frac{1}{2}$ Heisenberg antiferromagnetic chain compound ${\mathrm{BaNa}}_2\mathrm{Cu}{\left({\mathrm{VO}}_4\right)}_2$. This orthovanadate has a centrosymmetric crystal structure, $C2/c$, where the magnetic ${\mathrm{Cu}}^{2+}$ ions form spin chains. These chains are arranged in layers, with the chain direction changing by ${62}^{\circ }$ between the two successive layers. Alternatively, the spin lattice can be viewed as anisotropic triangular layers upon taking the interchain interactions into consideration. Despite this potential structural complexity, temperature-dependent magnetic susceptibility, heat capacity, electron spin resonance intensity, and nuclear magnetic resonance (NMR) shift agree well with the uniform spin-$1/2$ Heisenberg chain model with an intrachain coupling of $J/k_{\mathrm{B}}\simeq 5.6$ K. The saturation field obtained from the magnetic isotherm measurement consistently reproduces the value of $J/k_{\mathrm{B}}$. Further, the ${}^{51}\mathrm{V}$ NMR spin-lattice relaxation rate mimics the one-dimensional character in the intermediate temperature range, whereas magnetic long-range order sets in below $T_{\mathrm{N}}\simeq 0.25$ K. The effective interchain coupling is estimated to be $J_{\perp }/k_{\mathrm{B}}\simeq 0.1$ K. The theoretical estimation of exchange couplings using band-structure calculations reciprocate our experimental findings and unambiguously establish the one-dimensional character of the compound. Finally, the spin lattice of ${\mathrm{BaNa}}_2\mathrm{Cu}{\left({\mathrm{VO}}_4\right)}_2$ is compared with the chemically similar but not isostructural compound ${\mathrm{BaAg}}_2\mathrm{Cu}{\left({\mathrm{VO}}_4\right)}_2$.

We report very low-temperature measurements of ${}^{51}\mathrm{V}$ NMR spectra as a function of external magnetic field in the $s=1∕2$ Heisenberg triangular antiferromagnet cluster ${\mathrm{K}}_6\left[{\mathrm{V}}_{15}{\mathrm{As}}_6{\mathrm{O}}_{42}\left({\mathrm{H}}_2\mathrm{O}\right)\right]\bullet 8{\mathrm{H}}_2\mathrm{O}$ (V15), a simple prototype of a geometrically magnetic frustrated system. It is known that the frustration is relieved by a splitting of the degenerate ground state into two $S_T=1∕2$ states. Our measurements allow the microscopic determination of the local spin configuration both in the nonfrustrated total spin $S_T=3∕2$ state at high fields and in the two quasidegenerate $S_T=1∕2$ ground states at low fields, where it is shown that the simple frustrated chiral configuration in the triangle is broken down into two different spin configurations corresponding to the two quasidegenerate $S_T=1∕2$ states.