Abstract
We have grown La 1.37 Sr 1.63 Mn 2 O 7 single crystals with a laser-diode-heated floating-zone furnace and studied the crystallinity, structure, and magnetoresistance (MR) effect by in-house X-ray Laue diffraction, X-ray powder diffraction, and resistance measurements. The La 1.37 Sr 1.63 Mn 2 O 7 single crystal crystallizes into a tetragonal structure with space group I4/mmm at room temperature. At 0 T, the maximum resistance centers around ∼166.9 K. Below ∼35.8 K, it displays an insulating character with an increase in resistance upon cooling. An applied magnetic field of B = 7 T strongly suppresses the resistance indicative of a negative MR effect. The minimum MR value equals −91.23% at 7 T and 128.7 K. The magnetic-field-dependent resistance shows distinct features at 1.67, 140, and 322 K, from which we calculated the corresponding MR values. At 14 T and 140 K, the colossal negative MR value is down to −94.04(5)%. We schematically fit the MR values with different models for an ideal describing of the interesting features of the MR value versus B curves.
Highlights
During the past decades, the study of R1− x A x MnO3 materials, where R and A represent trivalent rare-earth and divalent alkaline-earth ions, respectively, and Mn ions locate at the center of O6 octahedra that build up a three-dimensional network in the way of sharing corners, has been performed intensively
The first-order phase transition from insulating to metallic behavior was confirmed by neutron scattering in the study of La2/3 Ca1/3 MnO3 compound [9]
Compared with the traditional floating-zone furnace with IR-heating halogen lamps, the laser-diode-heated floating-zone furnace holds a higher maximum temperature and a steeper temperature gradient at the liquid–solid interface [29]. These advantages are more favorable during the process of single crystal growth [15,30]
Summary
The study of R1− x A x MnO3 materials, where R and A represent trivalent rare-earth and divalent alkaline-earth ions, respectively, and Mn ions locate at the center of O6 octahedra that build up a three-dimensional network in the way of sharing corners, has been performed intensively. These compounds attracted considerable attention because they exhibit metal-insulator transitions, a colossal magnetoresistance (MR) effect, charge/orbital ordering, and other fascinating properties [1,2,3,4]. The Mn and Crystals 2020, 10, 547; doi:10.3390/cryst10060547 www.mdpi.com/journal/crystals
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