ABSTRACT
Geometrically frustrated lattices combined with magnetism usually host quantum fluctuations that suppress magnetic orders and generate highly entangled ground states. Three-dimensionally (3D) frustrated magnets generally exist in the diamond and pyrochlore lattices, while two-dimensionally (2D) frustrated geometries contain Kagomé, triangular, and honeycomb lattices. In this work, we reported using chemical pressure to tune the magnetism of the pyrochlore lattice in LiYbSe2 into a triangular lattice by doping Ga or In. Li3-xGaxYb3Se6 and Li3-xInxYb3-yInySe6/Li3-xInxYb3-yâ¡ySe6 crystallize in a trigonal α-NaFeO2 structure-type (space group R3Ì m) and can be synthesized using either LiCl or Se flux. In Li3-xGaxYb3Se6, Ga3+ and Li+ are mixed, leaving Yb3+ on the triangular plane. Instead of just Li+ being replaced in Li3-xGaxYb3Se6, In3+ was observed in both the Li+ and Yb3+ layers in Li3-xInxYb3-yInySe6 depending on the reaction conditions. Dominant antiferromagnetic interactions are revealed by magnetic measurements in both Li3-xGaxYb3Se6 and Li3-xInxYb3-yInySe6/Li3-xInxYb3-yâ¡ySe6. However, no long-range magnetic order is detected in thermomagnetic measurements above 1.8 K due to geometrical frustration. Thus, Li3-xGaxYb3Se6, Li3-xInxYb3-yInySe6/Li3-xInxYb3-yâ¡ySe6, and the LiYbSe2 previously discovered by our group provide an ideal platform to understand the complex structure-magnetism correlations from 3D to 2D frustrated lattices.
ABSTRACT
Three-dimensionally (3D) frustrated magnets generally exist in the magnetic diamond and pyrochlore lattices, in which quantum fluctuations suppress magnetic orders and generate highly entangled ground states. LiYbSe2 in a previously unreported pyrochlore lattice was discovered from LiCl flux growth. Distinct from the quantum spin liquid (QSL) candidate NaYbSe2 hosting a perfect triangular lattice of Yb3+, LiYbSe2 crystallizes in the cubic pyrochlore structure with space group Fd3m (No. 227). The Yb3+ ions in LiYbSe2 are arranged on a network of corner-sharing tetrahedra, which is particularly susceptible to geometrical frustration. According to our temperature-dependent magnetic susceptibility measurements, the dominant antiferromagnetic interaction in LiYbSe2 is expected to appear around 8 K. However, no long-range magnetic order is detected in thermomagnetic measurements above 70 mK. Specific heat measurements also show magnetic correlations shifting with applied magnetic field with a degree of missing entropy that may be related to the slight mixture of Yb3+ on the Li site. Such magnetic frustration of Yb3+ is rare in pyrochlore structures. Thus, LiYbSe2 shows promise in intrinsically realizing disordered quantum states like QSL in pyrochlore structures.
ABSTRACT
MnPd5Se, a derivative of the anti-CeCoIn5-type phase, was synthesized from a high-temperature solid-state reaction, structurally determined by X-ray diffraction, and magnetically characterized with a combined magnetic measurement and neutron powder diffraction (NPD). According to the X-ray diffraction results, MnPd5Se crystallizes in a layered tetragonal structure with the same space group as CeCoIn5, P4/mmm (No. 123). MnPd5Se shows antiferromagnetic ordering around 80 K on the basis of the magnetic property measurements. An A-type antiferromagnetic structure was revealed from the analysis of neutron powder diffraction results at 300, 50, and 6 K. Moreover, a spin orientation rotation was observed as the temperature decreased. Pd L3 X-ray absorption near edge spectroscopy results for MnPd5Se semiqualitatively correlate with the calculated density of states supporting a nominal 0.2 electron transfer into the Pd d orbital from either Se or Mn in the compound. The discovery of MnPd5Se, along with our previously reported MnT5Pn (T = Pd or Pt; Pn = P or As), provides a tunable system for studying the magnetic ordering from ferromagnetism to antiferromagnetism with the strong spin-orbit coupling effect.
