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arXiv · 1903.10987

Complex exchange mechanism driven ferromagnetism in half-metallic Heusler Co$_{2}$TiGe: Evidence from critical behavior

Shubhankar Roy·Nazir Khan·Ratnadwip Singha·Arnab Pariari·Prabhat Mandal
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Abstract

We have investigated the critical phenomenon associated with the magnetic phase transition in the half-metallic full-Heusler Co$_2$TiGe. The compound undergoes a continuous ferromagnetic to paramagnetic phase transition at the Curie temperature $T_{C}$=371.5 K. The analysis of magnetization isotherms in the vicinity of $T_{c}$, following modified Arrott plot method, Kouvel-Fisher technique, and critical isotherm plot, yields the asymptotic critical exponents $β$=0.495, $γ$=1.324, and $δ$=3.67. The self-consistency and reliability of the obtained exponents are further verified by the Widom scaling relation and scaling equation of states. The mean-field-like value of the critical exponent $β$ suggests long-range nature of the exchange interactions, whereas the values of the critical exponents $γ$ and $δ$, imply sizeable critical spin fluctuations. The half-metallic itinerant character of Co$_{2}$TiGe in the presence of magnetic inhomogeneity may result in such a strong deviation from the three-dimensional Heisenberg values ($β$=0.369, $γ$=1.38 and $δ$=4.8) of the critical exponents towards the mean field values ($β$=0.5, $γ$=1 and $δ$=3). The results suggest complex nature of exchange couplings that stabilize the long-range ferromagnetic ordering in the system and are consistent with the earlier theoretical studies on the exchange mechanism in Co$_2$TiGe.

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Shubhankar Roy, Nazir Khan, Ratnadwip Singha, Arnab Pariari, Prabhat Mandal. 2019-03-26. Complex exchange mechanism driven ferromagnetism in half-metallic Heusler Co$_{2}$TiGe: Evidence from critical behavior. https://doi.org/10.1103/physrevb.99.214414

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