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تسجيل مستخدم جديدSingle crystal investigation of proposed type-II Weyl semimetal CeAlGe
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We present details of materials synthesis, crystal structure, and anisotropic magnetic properties of single crystals of CeAlGe, a proposed type-II Weyl semimetal. Single-crystal x-ray diffraction confirms that CeAlGe forms in noncentrosymmetric I4$_1$md space group, in line with predictions of non-trivial topology. Magnetization, specific heat and electrical transport measurements were used to confirm antiferromagnetic order below 5 K, with an estimated magnon excitation gap of $Delta$ = 9.11 K from heat capacity and hole-like carrier density of 1.44 $times$ 10$^{20}$ cm$^{-3}$ from Hall effect measurements. The easy magnetic axis is along the [100] crystallographic direction, indicating that the moment lies in the tetragonal $it{ab}$-plane below 7 K. A spin-flop transition to less than 1 $mu_B$/Ce is observed to occur below 30 kOe at 1.8 K in the $M(H)$ ($bf{H}|bf{a}$) data. Small magnetic fields of 3 kOe and 30 kOe are sufficient to suppress magnetic order when applied along the $it{a}$- and $it{c}$-axes, respectively, resulting in a complex $it{T-H}$ phase diagram for $bf{H}|bf{a}$ and a simpler one for $bf{H}|bf{c}$.
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CeAlGe, a proposed type-II Weyl semimetal, orders antiferromagnetically below 5 K. Both a spin-flop and a spin-flip transitions to less than 1 $mu_B$/Ce are observed at 2 K below 30 kOe in the $M(H)$ ($bf{H}|bf{a}$ and $bf{b}$) and 4.3 kOe ($bf{H}|la
ngle110rangle$) data, respectively, indicating a four-fold symmetry of the $M(H)$ along the principal directions in the tetragonal $it{ab}$-plane with $langle110rangle$ set of easy directions. However, anomalously robust and complex two-fold symmetry is observed in the angular dependence of resistivity and magnetic torque data in the magnetically ordered state once the field is swept in the $it{ab}$-plane. This two-fold symmetry is independent of temperature- and field-hystereses and suggests a magnetic phase transition that separates two different magnetic structures in the $it{ab}$-plane. The boundary of this magnetic phase transition can be tuned by different growth conditions.
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