Czochralski growth, magnetic and magneto-optical properties of Na2Tb4(MoO4)7 crystal

• Na2Tb4(MoO4)7 crystals were grown by the Czochralski method.
• The magnetic property was characterized by magnetic susceptibility from 2 to 300 K.
• Na2Tb4(MoO4)7 shows a high transparency from 600 nm to 1500 nm.
• The Verdet constant of Na2Tb4(MoO4)7 is about 1.6 times as large as that of Tb3Ga5O12.

Na2Tb4(MoO4)7 crystals have been grown by the Czochralski technique for the first time for magneto-optical applications. Structure refinement of XRD data confirms that the compound crystallizes in the tetragonal system I41/a  , with scheelite structure. The as-grown crystal exhibits moderate thermal stability and weak thermal expansion anisotropy (αc/αa≈1.08αc/αa≈1.08), and the hardness is about 4.7 Moh. Transmittance spectra indicated that the Na2Tb4(MoO4)7 crystal presents a high transparency from 600 nm to 1500 nm after annealing in O2 atmosphere at 973 K for 20 h. The Faraday effect and the temperature dependence of the magnetic susceptibility have been investigated, which demonstrate that the Na2Tb4(MoO4)7 crystal exhibits paramagnetic behavior over the experimental temperature-range 2–300 K and yields a Faraday rotation which is about 1.6 times as large as that of Tb3Ga5O12 crystal. Na2Tb4(MoO4)7 crystal is therefore a promising Faraday material in particular for new magneto-optical applications in the visible–near IR wavelength region.