arXiv subjects

Harish Chandr Chauhan

Publications and source records attributed to Harish Chandr Chauhan.

4 recordsLinked to original sources

arXiv2025

New Methods for Critical Analysis: Revealing the Simultaneous Existence of Universality Classes in Nontrivial Magnetic Systems

In magnetic systems, the microscopic constituents exhibit power law behavior near the paramagnetic transition temperature, $T_C$. The critical exponents (CEs) associated with the physical quantities that demonstrate singular behavior at $T_C$ illustrate the critical behavior, specifically the range and type of exchange interactions emerging in magnetic systems. However, it is realized that the developed methodologies may not yield accurate values of CEs, especially for magnetic systems with competing interactions, referred to as nontrivial magnetic systems. Currently, no comprehensive method effectively addresses the competing effects of the range of magnetic interactions among the constituent entities emerging in such systems. Additionally, there is no definitive explanation for CE values that do not belong to any single universality class. Here, we present new methodologies for critical analysis aimed at determining both the range of exchange interaction(s) and appropriate values of CEs. Using computational and experimental investigations, we analyze the magnetic behavior of trivial Ni and nontrivial Gd. Our findings demonstrate that (i) the critical behavior remains the same on either side of $T_C$, (ii) the critical behavior associated with local electron moments remains unaffected by the magnetic field, and (iii) in Gd, the critical role of competing interactions becomes evident: local electron moments follow a three-dimensional Ising-type short-range interaction, while itinerant electron moments exhibit a mean-field-type long-range Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, which weakens under an external magnetic field due to the localization effect on itinerant electrons.

cond-mat.str-el↗

arXiv2023

Origin of magnetic anisotropy in $La_{(1\-x)}Sr_{x}MnO_{3}$

Here, we report the origin of magnetic anisotropy in Sr-doped infinite layer manganites $La_{(1\-x)}Sr_{x}MnO_{3}$ (0.125 \leq x \leq 0.400). Magnetic anisotropy is responsible for the large difference in the temperature dependence of field-cooled and zero-field-cooled magnetization. Translational symmetry breaking in the context of spins around the boundary between the ferromagnetic (FM) antiferromagnetic (AFM) region leads to FM-AFM interaction and results in magnetic anisotropy (exchange anisotropy). Here, we propose that FM-AFM interaction around the boundary between FM clusters or domains in the AFM background or between AFM clusters or domains in the ferromagnetic background is responsible for doping-dependent nonmonotonic behavior and the origin of magnetic anisotropy.

cond-mat.str-el↗

arXiv2020

Magnetism in quasi-two-dimensional tri-layer La$_{2.1}$Sr$_{1.9}$Mn$_3$O$_{10}$ manganite

The tri-layer La$_{3-3x}$Sr$_{1+3x}$Mn$_{3}$O$_{10}$ manganites of Ruddlesden-Popper (RP) series are naturally arranged layered structure with alternate stacking of m-MnO$_2$ (m = 3) planes and rock-salt type block layers (La, Sr)$_2$O$_2$ along c-axis. The dimensionality of the RP series manganites depends on the number of perovskite layers and significantly affects the magnetic and transport properties of the system. The tri-layer La$_{2.1}$Sr$_{1.9}$Mn$_{3}$O$_{10}$ shows second-order magnetic phase transition. The critical behavior of phase transition has been studied around the transition temperature (T$_C$) to understand the low dimensional magnetism in tri-layer La$_{2.1}$Sr$_{1.9}$Mn$_{3}$O$_{10}$ of the Ruddlesden-Popper series manganites. We have determined the critical exponents for tri-layer La$_{2.1}$Sr$_{1.9}$Mn$_{3}$O$_{10}$, which belong to the short-range two-dimensional (2D)-Ising universality class. The low dimensional magnetism in tri-layer La$_{2.1}$Sr$_{1.9}$Mn$_{3}$O$_{10}$ manganite is also explained with the help of renormalization group theoretical approach for short-range 2D-Ising systems. It has been shown that the layered structure of tri-layer La$_{2.1}$Sr$_{1.9}$Mn$_{3}$O$_{10}$ results in three different type of interactions intra-planer ($ J_{ab} $), intra-tri-layer ($ J_{c} $) and inter-tri-layer ($ J' $) such that $ J_{ab} $ $ > $ $ J_{c} $ $ >> $$ J' $ and competition among these give rise to the canted antiferromagnetic spin structure above T$ _{C} $. Based on the similar magnetic interaction in bi-layer manganite, we propose that the tri-layer La$_{2.1}$Sr$_{1.9}$Mn$_{3}$O$_{10}$ should be able to host the skyrmion below T$ _{C} $ due to its strong anisotropy and layered structure.

cond-mat.str-el↗

arXiv2019

Multiple phases with tricritical point and Lifshitz point in skyrmion host Cu$_2$OSeO$_3$

Magnetic skyrmions, a topologically stable spin swirling object, have attracted a great interest due to their potential applications in future spintronics and ultra high dense magnetic memory devices. Cu$_2$OSeO$_3$ is only known insulating chiral helimagnet with multiple phases including skyrmion phase. Existence of skyrmion phase as well as first and second order phase transitions make Cu$_2$OSeO$_3$ a promissing candidate for investigating complex magnetic phenomena. Here, we report that both first and second order magnetic phase transitions are responsible in determining the phase diagram with atleast two multicritical point in Cu$_2$OSeO$_3$. Fluctuation-induced first order transition is realized as a precursor for skyrmion phase over a small window of temperature of magnetic field. The evolution of field dependent entropy at the phase transition provides the evidence for tricritical point. Furthermore, existence of commensurate and incommensurate phases, alongwith co-existence of three second order phase transitions provide evidence for the existence of Lifshitz point.

cond-mat.str-el↗