Unusual Electrical and Magnetic Properties in Layered EuZn₂As₂

Abstract

Eu-based compounds often exhibit unusual magnetism, which is critical for nontrivial topological properties seen in materials such as EuCd 2 As 2 . The authors investigate the structure and physical properties of EuZn 2 As 2 through measurements of the electrical resistivity, Hall effect, magnetization, and neutron diffraction. Their data show that EuZn 2 As 2 orders antiferromagnetically with an A-type spin configuration below T N = 19 K. Surprisingly, there is strong evidence for dominant ferromagnetic fluctuations above T N , as reflected by positive Curie-Weiss temperature and extremely large negative magnetoresistance (MR) between T N and T fl ≈200 K. Furthermore, the angle dependence of the MR ab indicates field-induced spin reorientation from the ab-plane to a direction ≈45°from the ab plane. Compared to EuCd 2 As 2 , the doubled T N and T fl make EuZn 2 As 2 a better platform for exploring nontrivial magnetic and electronic properties in both magnetic fluctuation (T N < T < T fl ) and ordered (T < T N ) regimes.

Canted antiferromagnetic order in EuZn2As2 single crystals

“…It increases with decreasing temperature until the kink at temperature T N = 19.2 K is reached, where it first saturates and then slightly decreases, indicating a transition to antiferromagnetic (AFM) state. This temperature is close to that reported recently for polycrystalline 13 and single crystalline samples 14 . Panel (a) also presents the temperature dependence of the reciprocal magnetic susceptibility 1/ χ , showing a linear behavior above T N , together with the fit of the Curie–Weiss dependence: .…”

“…6 c). This discrepancy with respect to the A-type order proposed by Blawat et al 14 is consistent with difference in coupling between Eu magnetic moments, as indicated by a 50% higher paramagnetic Curie temperature in our case. Also the unit cell volume is larger (by 0.3%) in our case, which altogether can explain the different magnetic structures.…”

“…The M ( H ) dependences in panel d, show clear nonlinearities at low field for both orientations. In the recent study on EuZn 2 As 2 14 linear M ( H ) dependences were observed in the whole field range below saturation. This difference with respect to our results might be caused by different magnetic structure.…”

“…spin flop) 17 . Although Blawat et al 14 claim an A-type antiferromagnetic structure, no spin flop was observed for B ⊥ c either. In the inset of Fig.…”

“…This difference with respect to our results might be caused by different magnetic structure. In ref 14 the A-type antiferromagnetic magnetic structure was proposed (Fig. 6 a).…”