R. Rawat - IUC

R. Rawat
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R. Rawat
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IUC
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Physics - Strongly Correlated Electrons (31)
 
Physics - Materials Science (21)
 
Physics - Superconductivity (7)
 
Mathematics - Functional Analysis (2)
 
Physics - Physics Education (1)
 
Physics - Statistical Mechanics (1)
 
Physics - Mesoscopic Systems and Quantum Hall Effect (1)
 
Computer Science - Cryptography and Security (1)
 
Computer Science - Artificial Intelligence (1)

Publications Authored By R. Rawat

We investigate solving discrete optimisation problems using the estimation of distribution (EDA) approach via a novel combination of deep belief networks(DBN) and inductive logic programming (ILP).While DBNs are used to learn the structure of successively better feasible solutions,ILP enables the incorporation of domain-based background knowledge related to the goodness of solutions.Recent work showed that ILP could be an effective way to use domain knowledge in an EDA scenario. Read More

Co4Nb2O9 (CNO) having {\alpha}-Al2O3 crystal structure with Co chains along c-direction shows gigantic magnetoelelctric coupling below antiferromagnetic ordering temperature of 27 K but above a spin flop field of 1.6 T. We have investigated structural, magnetic and magnetoelectric properties of Fe substituted (10% and 20%) samples and compared with the parent one. Read More

Single phase polycrystalline sample of perovskite Sr2TiMnO6 (STMO) has been successfully synthesized via solid state reaction route. Its detailed structural and physical properties have been studied using x-ray diffraction, transmission electron microscopy, magnetization, specific heat, and dielectric measurements. Rietveld analysis of the powder XRD data and transmission electron microscopy studies confirm that STMO is not a double perovskite structure with Fm-3m space group. Read More

Novel thermal effects across the first order antiferromagnetic (AFM) - ferromagnetic (FM) transition in an intermetallic alloy are reported. They show instances of warming when heat is extracted from the sample, and cooling when heat is provided to the sample across AFM-FM transition in Ta doped $HfFe_2$, thus providing indisputable evidence of metastable supercooled AFM and superheated FM states, respectively. Such thermal effects in a magnetic solid prepared from commercially available materials has been reported for the first time. Read More

We have investigated the temperature evolution of magnetism and its interrelation with structural parameters in perovskite-based layered compound Sr$_2$IrO$_4$, which is believed to be a $J_{eff}$ = 1/2 Mott insulator. The structural distortion plays an important role in this material which induces a weak ferromagnetism in otherwise antiferromagnetically ordered magnetic state with transition temperature around 240 K. Interestingly, at low temperature below around 100 K, a change in magnetic moment has been observed. Read More

Nowadays smartphones come embedded with multiple motion sensors, such as an accelerometer, a gyroscope and an orientation sensor. With these sensors, apps can gather more information and therefore provide end users with more functionality. However, these sensors also introduce the potential risk of leaking a user's private information because apps can access these sensors without requiring security permissions. Read More

Large magnetocaloric effect (MCE) and magnetoresistance (MR) together with negligible hysteresis loss has been observed in ErNiSi compound, which undergoes metamagnetic transition at low temperatures. Magnetization, heat capacity and resistivity measurements confirm the metamagnetic transition. The maximum value of isothermal entropy change and MR for a field change of 50 kOe are found to be 19. Read More

Structural phase transition studies employing low-temperature transmission electron microscopy, and low-temperature x-ray diffraction have been carried out on nearly stoichiometric ({\delta}=0.01) and off-stoichiometric ({\delta}=0.12) versions of La0. Read More

Present study reveals that the free energy landscape of the La5/8-yPryCa3/8MnO3 (LPCMO) system could be modified by elastic strain interaction in the epitaxial thin films. Epitaxial LPCMO thin films of various thicknesses are grown on LaAlO3 substrate by pulsed laser deposition. With increasing thickness, by virtue of island growth morphology, strain disorder is invoked in thin films during strain relaxation process. Read More

We demonstrate interface energy level engineering, exploiting the modification in energy band structure across Verwey phase transition of $Fe_{3}O_{4}$ electrode, in a $Fe_{3}O_{4}$(111)/$Alq_{3}$/Co vertical spin-valve (SV) device. Experimental results on device characteristics I-V) study exhibit a transition in conduction mode from carrier injection to tunneling across Verwey transition temperature ($T_{V}$) of $Fe_{3}O_{4}$ electrode. Both giant magneto-resistance (GMR) and tunneling MR (TMR) have been observed in a single SV device as a function of temperature, below and above $T_{V}$, respectively. Read More

Low temperature high magnetic field $^{57}Fe$ M$\ddot{o}$ssbauer measurements were carried out on inter-metallic $Hf_{0.77}Ta_{0.23}Fe_2$ compound by following novel paths in H-T space. Read More

The effect of local structure on the magnetic and transport properties of the layered perovskites has been investigated. The samples PrBaCo$_{2}$O$_{5+\delta}$, ($\delta$ = 0.80 and 0. Read More

Magnetic behavior of the pseudo-binary alloy $Hf_{1-x}Ta_xFe_2$ has been studied, for which the zero field ferromagnetic (FM) to antiferromagnetic (AFM) transition temperature is tuned near to T=0 K. These alloys show anomalous thermomagnetic irreversibility at low temperature due to kinetic arrest of the first order AFM-FM transition. All the three studied compositions show re-entrant transition in zero field cooled warming curve and anomalous non-monotonic variation of upper critical field in isothermal magnetization. Read More

The magnetic field-pressure-temperature (H-P-T) phase diagram for first order antiferromagnetic (AFM) to ferromagnetic (FM) transition in Fe49(Rh0.93Pd0.07)51 has been constructed using resistivity measurements under simultaneous application of magnetic field (up to 8 Tesla) and pressure (up to 20 kbar). Read More

The unusual magnetoresistance (MR) behavior in Sr2FeMoO6, recently termed as spin-valve type MR (SVMR), presents several anomalies that are little understood so far. The difficulty in probing the origin of this phenomenon, arising from the magnetic property of only a small volume fraction of the ferromagnetic bulk, is circumvented in the present study by the use of ac susceptibility measurements that are sensitive to the slope rather than the magnitude of the magnetization. The present study unravels a spin-glass (SG) like surface layer around each soft ferromagnetic (FM) grain of Sr2FeMoO6. Read More

We present our study of effect of substrate induced strain on the La5/8-yPryCa3/8MnO3 (y=0.45), thin films grown on LaAlO3, NdGaO3 and SrTiO3 susbtrates that show large scale phase separation. It is observed that unstrained films grown on NdGaO3 behave quite similar to bulk material but the strained film grown on SrTiO3 show melting of insulating phase to metallic phase at low temperatures. Read More

The first order antiferromagnetic (AFM) to ferromagnetic (FM) transition in the functional material Fe49(Rh0.93Pd0.07)51 has been studied at low temperatures and high magnetic fields. Read More

Let $Z_{r,R}$ be the class of all continuous functions $f$ on the annulus $\Ann(r,R)$ in the real hyperbolic space $\mathbb B^n$ with spherical means $M_sf(x)=0$, whenever $s>0$ and $x\in \mathbb B^n$ are such that the sphere $S_s(x)\subset \Ann(r, R) $ and $B_r(o)\subseteq B_s(x).$ In this article, we give a characterization for functions in $Z_{r,R}$. In the case $R=\infty$, this result gives a new proof of Helgason's support theorem for spherical means in the real hyperbolic spaces. Read More

Glass-like arrest has recently been reported in various magnetic materials. As in structural glasses, the kinetics of a first-order transformation is arrested while retaining the higher-entropy phase as a non-ergodic state. We show visual mesoscopic evidence of the irreversible devitrification of the arrested antiferromagnetic-insulating phase in $Pr_{0. Read More

Let $Z(Ann(r,R))$ be the class of all continuous functions $f$ on the annulus $Ann(r,R)$ in $\mathbb C^n$ with twisted spherical mean $f \times \mu_s(z)=0,$ whenever $z\in \mathbb C^n$ and $s >0$ satisfy the condition that the sphere $S_s(z)\subseteq Ann(r, R) $ and ball $B_r(0)\subseteq B_s(z).$ In this paper, we give a characterization for functions in $Z(Ann(r,R))$ in terms of their spherical harmonic coefficients. We also prove support theorems for the twisted spherical means in $\mathbb C^n$ which improve some of the earlier results. Read More

Phase coexistence across disorder-broadened and magnetic-field-induced first order antiferromagnetic to ferrimagnetic transition in polycrystalline $Mn_{1.85}Co_{0.15}Sb$ has been studied mesoscopically by Scanning Hall Probe Microscope at 120K and up to 5 Tesla magnetic fields. Read More

We show that specific heat C$_p$ has non-Debye behavior for glassy states in half-doped manganites. Irrespective of the magnetic order or electronic states, these magnetic glasses have higher C$_p$ compared to their equilibrium counterparts. The excess C$_p$ contributed by the glassy state varies linearly with temperature similar to conventional glasses indicating tunneling in the two-level systems. Read More

Measurements of the critical current density (Jc) by magnetization and the upper critical field (Hc2) by magnetoresistance have been performed for hafnium-doped MgB2. There has been a remarkable enhancement of Jc as compared to that by ion irradiation without any appreciable decrease in Tc, which is beneficial from the point of view of applications. The irreversibility line extracted from Jc shows an upward shift. Read More

A negative-positive-negative switching behavior of magnetoresistance (MR) with temperature is observed in a ferromagnetic shape memory alloy Ni_1.75Mn_1.25Ga. Read More

The enhancement of the critical current density (Jc(H)) of carbon and nano-SiC doped MgB2 is presented and compared. The upper critical field (Hc2) being determined from resistivity under magnetic field experiments is though improved for both C substitution and nano-SiC addition the same is more pronounced for the former. In MgB2-xCx carbon is substituted for boron that induces disorder in the boron network and acts as internal pinning centres. Read More

A detailed investigation of first order ferrimagnetic (FRI) to antiferromagnetic (AFM) transition in Co (15%) doped $Mn_2Sb$ is carried out. These measurements demonstrate anomalous thermomagnetic irreversibility and glass-like frozen FRI phase at low temperatures. The irreversibility arising between the supercooling and superheating spinodals is distinguised in an ingenious way from the irreversibility arising due to kinetic arrest. Read More

Magnetic and transport properties of Ti substituted La$_{0.67}$Sr$_{0.33}$MnO$_3$ are drastically affected with a change in preparation conditions. Read More

Experiments on the oscillatory motion of a suspended bar magnet throws light on the damping effects acting on the pendulum. The viscous drag offered by air was found the be the main contributor for slowing the pendulum down. The nature and magnitude of the damping effects were shown to be strongly dependent on the amplitude. Read More

A detailed investigation of the first order antiferromagnetic insulator (AFI) to ferromagnetic metal (FMM) transition in $Nd{_{0.5}}Sr{_{0.5}}MnO{_{3}}$ is carried out by resistivity and magnetization measurements. Read More

We report phase formation, and detailed study of magnetization and resistivity under magnetic field of MgB2 polycrystalline bulk samples prepared by Fe-tube encapsulated and vacuum (10-5 torr) annealed (750 0C) route. Zero-field-cooled magnetic susceptibility (cZFC) measurements exhibited sharp transition to superconducting state with a sizeable diamagnetic signal at 39 K (Tc). The measured magnetization loops of the samples, despite the presence of flux jumps, exhibited a stable current density (Jc) of around 2. Read More

This is the first report of the observation of the onset of excess volume and also of the strain along the a-axis near the magnetic ordering temperature in Ru-1222 superconductor, and indicates a coupling between the lattice and the magnetism in this system. Magnetization, magneto transport and thermoelectric power measurements being carried out on the same sample are also reported. Read More

2006Jan
Affiliations: 1NPL, INDIA, 2NPL, INDIA, 3NPL, INDIA, 4IUC-Indore, INDIA, 5IUC-Indore, INDIA, 6Univ. TURKU, FINLAND, 7Univ. TURKU, FINLAND, 8Univ. TURKU, FINLAND

Magnetic susceptibility, M-H plot, magnetoresistance and thermoelectric power of the RuSr2Eu1.5Ce0.5Cu2O10 superconductor are measured. Read More

In this paper, we examine the possible influence of extrinsic factors on the electrical and magnetotransport of La(0.67)Ca(0.33)Mn(1-x)Ru(x)O(3) (x < 0. Read More

5% negative magnetoresistance (MR) at room temperature has been observed in bulk Ni_{2+x}Mn_{1-x}Ga. This indicates the possibility of using Ni_{2+x}Mn_{1-x}Ga as magnetic sensors. We have measured MR in the ferromagnetic state for different compositions (x=0-0. Read More

2004Aug
Affiliations: 1NPL, India, 2NPL, India, 3NPL, India, 4NPL, India, 5NPL, India, 6IUC, Indore, India, 7IUC, Indore, India, 8IUC, Indore, India, 9TIFR, Mumbai, India, 10TIFR, Mumbai, India

Samples of Y0.4Pr0.6Ba2-xSrxCu3O7 have been synthesized by a solid- state reaction route. Read More

The effect of plasma irradiation is studied systematically on a 4H polytype (002) oriented ${\rm CdI_2}$ stoichiometric film having compressive residual stress. Plasma irradiation was found to change the orientation to (110) of the film at certain moderate irradiation distances. A linear decrease in grain size and residual stress was observed with decreasing irradiation distance (or increasing ion energy) consistent with both structural and morphological observations. Read More

2003Aug
Affiliations: 1Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India, 2Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India, 3Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India, 4Inter University Consortium for DAE Facilities, Kandwa Road, Indore, India, 5Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India, 6Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India, 7Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India

This paper is in continuation of our previous work on the structural, electrical and magnetic properties of Ru doped La(0.67)Ca(0.33)MnO(3) compounds (Ref. Read More

2001May
Affiliations: 1Department of Physics, Indian Instiute of Science, Bangalore, INDIA, 2Department of Physics, Indian Instiute of Science, Bangalore, INDIA, 3Inter University Consortium for DAE facilities, Indore, INDIA, 4Inter University Consortium for DAE facilities, Indore, INDIA, 5CSIR Center of Excellence in Chemistry, Jawaharlal Nehru Center for Advanced Scientific Research, Bangalore, INDIA

We present the results of a study of specific heat on a single crystal of Pr$_{0.63}$Ca$_{0.37}$MnO$_3$ performed over a temperature range 3K-300K in presence of 0 and 8T magnetic fields. Read More

We report observation of substantial thermal relaxation in single crystal of charge ordered system Pr$_{0.63}$Ca$_{0.37}$MnO$_3$ in an applied magnetic field of H = 8T. Read More

2000Jun
Affiliations: 1SSCU, Indian institute of science, Bangalore, India, 2SSCU, Indian institute of science, Bangalore, India, 3SSCU, Indian institute of science, Bangalore, India, 4SSCU, Indian institute of science, Bangalore, India

Thin films of Pr0.7Ca 0.3MnO3, Nd-0. Read More