Nickel substitution induced reentrant spin glass behavior in EuGa4

Abstract

Typically, atomic scale disorder is essential to show glassy behavior and amorphous materials can be the optimum candidates in this regard. Generating local disorder in an ordered material by substitution of another metal is a challenging task. In this paper, we successfully substituted Ni in ${\mathrm{EuGa}}_{4}$ (${\mathrm{EuNi}}_{0.37}{\mathrm{Ga}}_{3.63}$) to induce spin glass (SG) behavior. The compound was characterized by single-crystal x-ray diffraction, dc magnetization, frequency-dependent ac susceptibility, isothermal magnetization at various temperatures, spin relaxation, specific heat, and electric resistivity. Two distinct anomalies were observed in dc susceptibility $\ensuremath{\sim}16.5$ and 5.2 K corresponding to long-range antiferromagnetic (AFM) ordering and SG transition, respectively. Their characteristic peaks in specific heat capacity further support the AFM and SG behavior. The irreversibility temperature is fitted with the Almeida-Thouless equation, confirming the Ising SG. The SG behavior is further confirmed by shift of maxima to a high temperature in ac susceptibility with increasing frequency. Nonzero spin relaxation after 7200 s, fitted with stretched exponential model, provides the value of $\ensuremath{\beta}=0.41$. This material can be identified as a possible reentrant SG as AFM and SG behavior coexist in the low-temperature range. Additionally, a spin-flip transition is observed in the AFM region ($5.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}<T<16.5\phantom{\rule{0.28em}{0ex}}\mathrm{K}$). Our first-principles calculations show Ni substitution induces the distortion in electronic band structure as compared with parent ${\mathrm{EuGa}}_{4}$. A minimal difference between the different magnetic configurations for Ni-substituted ${\mathrm{EuGa}}_{4}$ suggests the frustration in the lattice, pointing toward SG behavior.