Ultrasensitive multi-mode ESR probed ferromagnetic two-level system of $Mn^{4+}$ impurity ion in the insulated $MnO_6$ complex of $SrLaAlO_4$ at $20~mK$

TL;DR

This study uses ultrasensitive multi-mode ESR spectroscopy at 20 mK to investigate ferromagnetic states of $Mn^{4+}$ ions in $SrLaAlO_4$, revealing complex electronic hybridization and a giant g-factor associated with a two-level system.

Contribution

It demonstrates the detection of ferromagnetic states and electronic hybridization in $Mn^{4+}$ ions using advanced ESR techniques at ultra-low temperatures.

Findings

Ferromagnetic states of $Mn^{4+}$ ions identified.

Giant g-factor observed due to ferromagnetic impedance.

Evidence of Pseudo Jahn-Teller effect and structural instability.

Abstract

Ultrasnsitive multi-mode electron spin resonance spectroscopy in the $SrLaAlO_4$ dielectric resonator at $20~mK$ reveals ferromagnetic states of $Mn^{4+}$ impurity ion. The formation of ferromagnetic states in the $MnO_6$ complex implies to oxygen deficiency of this multi-valence $Mn^{4+}$ ion. Experiment results supports that an intricate electronic hybridization in $MnO_6$ structural instability is related to Pseudo Jahn-Teller effect. Measured dipolar hyperfine structure parameter of nucleus is $P_{\scriptscriptstyle\parallel} =-3.7\times 10^{-4}~cm^{-1}$. Mean inverse third power of the electron distance is $\langle r_q^{-3}\rangle=3.325~a.u.$ assuming nuclear electric quadruple moment $Q=+0.33(1)~barn$. In such a state, giant g-factor is observed due to magneto (ferromagnetic) impedance taking in to account a two-level system on the adiabatic-potential-energy-surface. The spins exhibited parity is opposite in the interaction of highest-occupied-molecular-orbital and lowest-unoccupied-molecular-orbital coupling.