Van der Waals (vdWs) crystals have attracted a great deal of scientific attention due to their interesting physical properties and widespread practical applications. Among all, CrSiTe3 (CST) is a ferromagnetic semiconductor with the Curie temperature (TC) of ~32 K. In this letter, we study the magnetic properties of bulk CST single crystal upon proton irradiation with the fluence of 1×10 18 protons/cm 2 . Most significantly, we observed an enhancement (23%) in the saturation magnetization from 3.9 µB to 4.8 µB, and is accompanied by an increase in coercive field (465-542 Oe) upon proton irradiation. Temperature dependent X-band electron paramagnetic resonance measurements show no additional magnetically active defects/vacancies that are generated upon proton irradiation. The findings from X-ray photoelectron spectroscopy and Raman measurements lead us to believe that modification in the spin-lattice coupling and introduction of disorder could cause enhancement in saturation magnetization. This work demonstrates that proton irradiation is a feasible method in modifying the magnetic properties of vdWs crystals, which represents a significant step forward in designing future spintronic and magneto-electronic applications. *
The critical phenomena and magnetic entropy of the quasi-2D ferrimagnetic crystal, Mn3Si2Te6 (MST), is analyzed along the easy axis (H || ab) as a function of proton irradiance. The critical exponents β and γ do not fall into any particular universality class upon proton irradiation. However, for pristine and irradiated samples, the critical exponents lie closer to mean field-like interactions; therefore, long-range interactions are presumed to be sustained in MST. The effective spatial dimensionality reveals that MST remains at d=3 under proton irradiation, whereas spin dimensionality transitions from an initial n=1 to n=2 and n=3 for 1 × 1015 and 5 × 1015 H+/cm2, indicating XY and Heisenberg interactions, respectively. The spin correlation function reveals an increase in magnetic correlations at 5 × 1015 H+/cm2. Maximum change in magnetic entropy at 3 T is the largest for 5 × 1015 H+/cm2 at 2.45 J/kg K, in comparison to 1.60 J/kg K for pristine MST. These results intriguingly align with previous findings on MST where magnetization increased by ∼50% at 5 × 1015 H+/cm2, in comparison to its pristine counterpart [Martinez et al., Appl. Phys. Lett. 116, 172404 (2020)]. Magnetic entropy derived from heat capacity analysis shows no large deviations across the proton irradiated samples suggesting that the antiferromagnetic (AFM) coupling between the Mn sites is stable even after proton irradiation. This implies that magnetization is enhanced through a strengthening of the super-exchange interaction between Mn atoms mediated through Te rather than a weakening of the AFM component.
The bulk van der Waals crystal Mn3Si2Te6 (MST) has been irradiated with a proton beam of 2 MeV at a fluence of 1×1018 H+ cm-2. The temperature dependent magnetization measurements show a drastic decrease in the magnetization of 49.2% in the H//c direction observed in ferrimagnetic state. This decrease in magnetization is also reflected in the isothermal magnetization curves. No significant change in the ferrimagnetic transition temperature (75 K) was reflected after irradiation. Electron paramagnetic resonance (EPR) spectroscopy shows no magnetically active defects present after irradiation. Here, experimental findings gathered from MST bulk crystals via magnetic measurements, magnetocaloric effect, and heat capacity are discussed.
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