Quantum Magnetic Properties in Perovskite with Anderson Localized Artificial Spin‐1/2

Abstract

Quantum magnetic properties in a geometrically frustrated lattice of spin‐1/2 magnet, such as quantum spin liquid or solid and the associated spin fractionalization, are considered key in developing a new phase of matter. The feasibility of observing the quantum magnetic properties, usually found in geometrically frustrated lattice of spin‐1/2 magnet, in a perovskite material with controlled disorder is demonstrated. It is found that the controlled chemical disorder, due to the chemical substitution of Ru ions by Co‐ions, in a simple perovskite CaRuO3 creates a random prototype configuration of artificial spin‐1/2 that forms dimer pairs between the nearest and further away ions. The localization of the Co impurity in the Ru matrix is analyzed using the Anderson localization formulation. The dimers of artificial spin‐1/2, due to the localization of Co impurities, exhibit singlet‐to‐triplet excitation at low temperature without any ordered spin correlation. The localized gapped excitation evolves into a gapless quasi‐continuum as dimer pairs break and create freely fluctuating fractionalized spins at high temperature. Together, these properties hint at a new quantum magnetic state with strong resemblance to the resonance valence bond system.

Quantum magnetic properties and metal-to-insulator transition in chemically doped calcium ruthenate perovskite

“…Metal-insulator transition in Ca(Co x Ru 1−x )O 3 : While the study of Ca(Ir x Ru 1−x )O 3 has provided valuable insight in understanding the novel metal-insulator transition phenomena in 113ruthenate perovskite, theoretical calculations hinted that substitution of Ru ion by isoelectronic Co-ion can lead to the formation of artificial spin-1/2 state in Ca(Co x Ru 1−x )O 3 . [25] Moreover, the non-stoichiometric composition of calcium ruthenate also manifest strong metal-insulator transition process, see Fig. 4.…”

“…[14,[19][20][21] Chemical substitution on Ca or Ru site is known to cause metal-insulator transition with complex magnetic properties, including spin glass and spin liquid phenomena. [11,[22][23][24][25][26] Here, we briefly discuss electrical, magnetic and spin-spin correlation properties in stoichiometric CaRuO 3 and some of the chemically doped versions.…”

“…Interestingly, the Co-Co interaction dominates the Ru-Co or Ru-Ru interaction in Ca(Co x Ru 1−x )O 3 . [25] Dimer formation and singlet-to-triplet transi- The substitution of Ru ion by Co ion generates a random distribution of artificial spin-1/2 moments. As described schematically in Fig.…”

Nonconventional magnetic phenomena in neodymium thin film

“…Therefore, electrical conduction, in the temperature range of 18 K < T < 25 K, may be occurring due to the hopping of charge carriers. On the other hand, the positive value of MR is argued to be arising due to the thermally activated mechanism in magnetic systems [26]. However, this argument is not applicable to electrical resistance temperature dependence below T 18 K in the Nd thin film, as it does not manifest exponential rise as a function of (reducing) temperature.…”

Nonconventional magnetic phenomena in neodymium thin film

“…On the other hand, the positive value of MR is argued to be arising due to the thermally activated mechanism in magnetic systems. [24] However, this argument is not applicable to electrical resistance temperature dependence below T 18 K in Nd thin film, as it does not manifest exponential rise as a function of (reducing) temperature. Rather, resistance flattens at lower temperature.…”