Magnetic anisotropy and spin dynamics in the kagome magnet Fe4Si2Sn7O16: NMR and magnetic susceptibility study on oriented powder

Fe4Si2Sn7O16 hosts an undistorted kagome lattice of Fe2+ (3d(6), S = 2) ions. We present results of bulk magnetization and Sn nuclear magnetic resonance (NMR) measurements on an oriented Fe4Si2Sn7O16 powder sample oriented in geometries parallel (parallel to) and perpendicular (perpendicular to) to the external applied magnetic field used for orienting the powder (B-ori). The bulk susceptibility. shows a broad peak at T-N similar to 3 K associated with antiferromagnetic ordering. NMR spectra indicate the presence of planar anisotropy in the kagome planes. From an analysis of the static NMR shift (K) and dynamic spin-lattice relaxation rate (1/T-1) we conclude the presence of dominant magnetic fluctuations in the kagome planes. For the parallel to orientation, K scales linearly with the bulk susceptibility for temperatures down to similar to 4 K, while in the. orientation K starts to deviate strongly below T similar to 30 K. We associate this deviation with the onset of spin-tilting towards the kagome planes. These correlations are also reflected in the 1/T-1 data for the parallel to orientation, which starts to decrease below T similar to 30 K. In this correlated regime, T-N < T < similar to 30 K, we discuss the formation of positive chiral spin correlations in the kagome planes.

Automated summary

Fe4Si2Sn7O16 hosts an undistorted kagome lattice of Fe2+ (3d(6), S = 2) ions. Results show the presence of planar anisotropy in the kagome planes, with dominant magnetic fluctuations in these planes indicated by static NMR shift (K) and dynamic spin-lattice relaxation rate (1/T-1) analysis.