Data for Paper "Microwave response of the chiral helimagnetic MnNb3S6"

Single-crystals of MnNb3S6 were grown by the chemical vapor transport (CVT) method. The powders of Mn, Nb, and S in high purity (99.9 %) were sealed in silica tube, which was heated to 800 ◦C. The two ends of the tube are kept at 800 ◦C and 950 ◦C respectively for several days. The I2 was used as the transport gas. The sample preparation method, chemical compositions, determination of crystal orientations were described in details elsewhere [1]. The magnetization was measured using a Quantum Design vibrating sample magnetometer (SQUID-VSM). The ESR spectra were carried out using a Bruker EMX plus model spectrometer operating at X-band frequencies (9.4 GHz). The applied magnetic field was rotated from the ab-plane to the c-axis. To ensure a precise magnetic field and data, the magnetic field was applied with no-overshoot mode, and relaxed for 2 minutes before data collection. The ESR spectra were collected at selected temperatures, where the variation of temperature was performed by a helium continuous flow thermostat.