Temperature-dependent magnetic anisotropy in the layered magnetic semiconductors CrI3 and CrBr3

Abstract

Chromium trihalides are layered and exfoliable semiconductors and exhibit unusual magnetic properties with a surprising temperature dependence of the magnetization. By analyzing the evolution of the magnetocrystalline anisotropy with temperature in chromium iodide CrI 3 , we find it strongly changes from K u = 300 ± 50 kJ/m 3 at 5 K to K u = 43 ± 7 kJ/m 3 at 60 K, close to the Curie temperature. We draw a direct comparison to CrBr 3 , which serves as a reference, and where we find results consistent with literature. In particular, we show that the anisotropy change in the iodide compound is more than 3 times larger than in the bromide. We analyze this temperature dependence using a classical model, showing that the anisotropy constant scales with the magnetization at any given temperature below the Curie temperature, indicating that the temperature dependence can be explained by a dominant uniaxial anisotropy where this scaling results from local spin clusters having thermally induced magnetization directions that deviate from the overall magnetization.

Distinct spin–lattice and spin–phonon interactions in monolayer magnetic CrI3

“…Therefore, according to Hund's rule, the three electrons occupying the t 2g triplet will have S = 3/2, which gives an atomic magnetic moment of 3 µ B . This picture is consistent with the observed saturation magnetization of bulk CrI 3 [31].…”

Magnetic anisotropy and low-field magnetic phase diagram of the quasi-two-dimensional ferromagnet Cr2Ge2Te6

“…The observed power law behavior fits well for uniaxial anisotropy models with a small deviation at higher temperatures, which can most probably be attributed to changes of K U itself due to temperature dependent anisotropic lattice deformations. A similar anisotropic anomaly was observed for CrX 3 (with X = Br, I) and also discussed in terms of interplay between K U,ef f and temperature 30 . All these compounds share the same magnetic ion and easy axis c ferromagnetic ordering together with a similar 2D honeycomb lattice.…”

“…For CrX 3 (X = Br, I) a similar analysis of K U,ef f (T ) was performed 30 . While the magnetocrystalline anisotropy constants of the chromium halides are larger than the one found for Cr 2 Ge 2 Te 6 (shown in Tab.…”

Magnetic anisotropy and spin-polarized two-dimensional electron gas in the van der Waals ferromagnet Cr2Ge2Te6

“…For magnetic fields applied perpendicular to the c axis a maximum of the magnetization is observed around 40 K, whereas magnetization increases monotonously with decreasing temperature for H c. A similar difference between measurements with fields perpendicular and parallel to the easy direction was found in other Cr-based 2D honeycomb materials, for example CrCl 3 [34] and CrI 3 [35,36]. This behavior might be caused either by antifer- romagnetic couplings between the ferromagnetic layers, a more complex ferromagnetic state in low magnetic fields or a temperature dependence of the magnetic anisotropy [34][35][36]. On the other hand, for a field of 3 T, which is larger than the low-temperature saturation fields for both orientations in Cr 2 Ge 2 Te 6 , an isotropic behavior was found with the onset of ferromagnetic (FM) correlations being shifted to higher temperatures as the external magnetic field enhances FM correlations.…”