Magnetocrystalline anisotropy in the Kondo-lattice compound CeAgAs2

Abstract

We report on the single crystal growth and anisotropic physical properties of CeAgAs2. The compound crystallizes as on ordered variant of the HfCuSi2-type crystal structure and adopts the orthorhombic space group P mca (#57) with two symmetry inequivalent cerium atomic positions in the unit cell. The orthorhombic crystal structure of our single crystal was confirmed from the powder x-ray diffraction and from electron diffraction patterns obtained from the transmission electron microscope. The anisotropic physical properties have been investigated on a good quality single crystal by measuring the magnetic susceptibility, isothermal magnetization, electrical transport and heat capacity. The magnetic susceptibility and magnetization measurements revealed that this compound orders antiferromagnetically with two closely spaced magnetic transitions at TN1 = 6 K and TN2 = 4.9 K. Magnetization studies have revealed a large magnetocrystalline anisotropy due to the crystalline electric field (CEF) with an easy axis of magnetization along the [010] direction. The magnetic susceptibility measured along the [001] direction exhibited a broad hump in the temperature range 50 to 250 K, while typical Curie-Weiss behaviour was observed along the other two orthogonal directions. The electrical resistivity and the heat capacity measurements revealed that CeAgAs2 is a Kondo lattice system with a magnetic ground state.

Antiferromagnetic Ordering and Transport Anomalies in Single-Crystalline CeAgAs2

“…The antiferromagnetic ordering manifests itself as a maximum in the magnetic susceptibility, a λ-like anomaly in the specific heat, and a distinct maximum in the electrical resistivity. At odds with the recent literature data [12], a single antiferromagnetic phase transition at T N = 4.9 K was found. At T = 1.72 K, the compound exhibits a metamagnetic transformation in a magnetic field of 0.5 T oriented perpendicular to [010] axis of the orthorhombic unit cell.…”

“…The least-square fit of Equation 1to the experimental data with fixed γ 4 f value yielded the parameters: a = 64.7 J mol −1 K −0.5 and ∆ = 7.1 K. The moderately enhanced value of γ 4 f , being close to that given in Ref. [12], manifests the importance of strong electronic correlations in the compound studied. Remarkably, the energy gap ∆ has magnitude similar to the Néel temperature of CeAgAs 2 .…”

Anisotropic and extreme magnetoresistance in the magnetic semimetal candidate erbium monobismuthide

“…where C e , C l , and C m represent the electronic, lattice, and spin contributions, respectively [38]. The inset of Fig.…”

“…The inset of Fig. 2(a) shows the specific heat of LuBi in temperature range from 2 to 20 K and its fit (the red line) with the expression C P = γ T + βT 3 [38], from which the Sommerfeld coefficient γ is determined as 0.3 mJ/K 2 mol, being of the same order of magnitude as for LaBi (0.85 mJ/K 2 mol) [39] and β has a value of 1.2 mJ/K 4 mol. Generally, the lattice contribution can be simply understood by the Debye model with the temperature-independent Debye temperature D [40].…”

“…Here, the nonmagnetic (C e + C l ) part of specific heat for ErBi is assumed to approximate the total specific heat of LuBi. Obviously, the magnetic contribution extends for temperature above 30 K ( T N ), exhibiting a pronounced maximum at T N associated with bulk magnetic order due to the Ruderman-Kittel-Kasuya-Yosida exchange interaction and a broad bump derived from Schottky anomalies [38]. Due to the antiferromagnetic order and broad peak associated with CEF effect, γ for ErBi cannot be simply estimated from the relation C P = γ T + βT 3 [42].…”