[Paper Review] Optical, transport and magnetic properties of new compound CeCd3P3

Shohei Higuchi, Yuki Noshima+3 more|arXiv (Cornell University)|Apr 14, 2016

Rare-earth and actinide compounds1 references3 citations

TL;DR

This study reports the synthesis and characterization of CeCd3P3, a new hexagonal ScAl3C3-type semiconductor with geometrically frustrated Ce3+ ions. The compound exhibits a fundamental band gap of ~0.75 eV, localized 4f electrons without long-range magnetic order down to 0.48 K, and magnetic susceptibility consistent with a quantum spin liquid candidate due to strong geometrical frustration and a large negative Weiss temperature (-60 K).

ABSTRACT

We have found that CeCd$_{3}$P$_{3}$ crystallizes into a hexagonal ScAl$_{3}$C$_{3}$-type structure. The optical, transport and magnetic properties of CeCd$_{3}$P$_{3}$ were investigated by measuring the diffuse reflectance, electrical resistivity and magnetization. CeCd$_{3}$P$_{3}$ is a semiconductor with the fundamental band gap of approximately 0.75 eV. The 4$f$ electrons of Ce$^{3+}$ ions are well localized but do not show long range order down to 0.48 K, presumably due to the geometrical frustration of Ce atoms. The magnetic ordering temperature is possibly lower than that of isostructural CeZn$_{3}$P$_{3}$ (0.75 K). Because several $f$-electron compounds with the ScAl$_{3}$C$_{3}$-type structure are quantum spin systems, CeCd$_{3}$P$_{3}$ may be a candidate of quantum spin liquid. On the other hand, the relatively large band gap compared to approximately 0.4 eV in CeZn$_{3}$P$_{3}$, would not be intimate with the observation of photoinduced Kondo effect, providing a potentially new range of applications of devices based on the Kondo effect.

Motivation & Objective

• To investigate the optical, transport, and magnetic properties of the new compound CeCd3P3.
• To determine whether CeCd3P3 exhibits quantum spin liquid behavior due to geometrical frustration of Ce3+ ions in a triangular lattice.
• To compare CeCd3P3 with isostructural CeZn3P3 and Ce2Sn2O7 to assess its potential for hosting quantum spin liquid or photoinduced Kondo effects.
• To evaluate the role of crystal structure and lanthanide contraction on electronic and magnetic properties in rare-earth-based semiconductors.

Proposed method

• Synthesized polycrystalline CeCd3P3 and LaCd3P3 via solid-state reaction in evacuated quartz tubes at 800 °C for 2 days.
• Performed X-ray diffraction (XRD) to confirm the ScAl3C3-type hexagonal structure and detect parasitic phases.
• Measured diffuse reflectance spectra to determine the optical band gap using UV-Vis spectroscopy.
• Measured electrical resistivity via the DC four-probe method from 20 to 300 K.
• Measured temperature-dependent magnetization (χ(T)) from 0.48 K to 300 K under 100 Oe to assess magnetic ordering and Curie-Weiss behavior.
• Analyzed crystal field effects using Stevens operators under D3d symmetry to interpret the ground state doublet and magnetization behavior.

Experimental results

Research questions

• RQ1 Does CeCd3P3 exhibit long-range magnetic order down to 0.48 K, or is it a quantum spin liquid candidate due to geometrical frustration?
• RQ2 How does the fundamental band gap of CeCd3P3 compare to that of CeZn3P3, and what implications does this have for the photoinduced Kondo effect?
• RQ3 What is the nature of the 4f electron state in CeCd3P3, and how does it compare to the CEF ground state in Ce2Sn2O7?
• RQ4 How does the ionic radius of Cd compared to Zn affect the magnetic ordering temperature in ScAl3C3-type Ce compounds?
• RQ5 What role does the D3d point symmetry at the Ce site play in stabilizing a quantum spin liquid ground state?

Key findings

• CeCd3P3 crystallizes in the hexagonal ScAl3C3-type structure with lattice parameters a = 4.28251(62) Å and c = 21.00239(230) Å.
• The fundamental band gap of CeCd3P3 is 0.75 eV, larger than the ~0.4 eV gap in CeZn3P3.
• The magnetic susceptibility follows the Curie-Weiss law above 50 K with an effective moment of 2.77 μB/Ce and a Weiss temperature of -60 K.
• No long-range magnetic order is observed down to 0.48 K, with a possible magnetic transition at ~1.5 K attributed to magnetic impurities.
• The magnetization at 0.48 K remains paramagnetic up to 1 T, supporting the absence of long-range order and suggesting a quantum spin liquid candidate.
• The CEF ground state is a linear combination of |±1/2⟩ and |∓5/2⟩ states under D3d symmetry, similar to Ce2Sn2O7, which is a known quantum spin liquid candidate.