Magnetic ground state of the multiferroic hexagonal LuFeO3

Suresh, Pittala,Vijaya Laxmi, K.,Bera, A. K.,Yusuf, S. M.,Chittari, Bheema Lingam,Jung, Jeil,Anil Kumar, P. S. American Physical Society 2018 Physical Review B Vol.97 No.18

<P>The structural, electric, and magnetic properties of bulk hexagonal LuFeO3 are investigated. Single phase hexagonal LuFeO3 has been successfully stabilized in the bulk form without any doping by sol-gel method. The hexagonal crystal structure with P6(3)cm space group has been confirmed by x-ray-diffraction, neutron-diffraction, and Raman spectroscopy study at room temperature. Neutron diffraction confirms the hexagonal phase of LuFeO3 persists down to 6 K. Further, the x-ray photoelectron spectroscopy established the 3+ oxidation state of Fe ions. The temperature-dependent magnetic dc susceptibility, specific heat, and neutron-diffraction studies confirm an antiferromagnetic ordering below the Neel temperature (T-N) similar to 130 K. Analysis of magnetic neutron-diffraction patterns reveals an in-plane (ab-plane) 120 degrees antiferromagnetic structure, characterized by a propagation vector k = (0 0 0) with an ordered moment of 2.84 mu(B)/Fe3+ at 6 K. The 120 degrees antifferomagnetic ordering is further confirmed by spin-orbit coupling density functional theory calculations. The on-site coulomb interaction (U) and Hund's parameter (J(H)) on Fe atoms reproduced the neutron-diffraction Gamma(1) spin pattern among the Fe atoms. P-E loop measurements at room temperature confirm an intrinsic ferroelectricity of the sample with remnant polarization P-r similar to 0.18 mu(C) cm(2). A clear anomaly in the dielectric data is observed at similar to T-N revealing the presence of magnetoelectric coupling. A change in the lattice constants at T-N has also been found, indicating the presence of a strong magnetoelastic coupling. Thus a coupling between lattice, electric, and magnetic degrees of freedom is established in bulk hexagonal LuFeO3.</P>

Effect of Curcumin on Intracerebroventricular Colchicine-Induced Cognitive Impairment and Oxidative Stress in Rats

Anil Kumar,P.S. Naidu,N. Seghal,S.S.V. Padi 한국식품영양과학회 2007 Journal of medicinal food Vol.10 No.3

This study was designed to investigate the protective effects of curcumin against colchicine-induced cognitiveimpairment and oxidative stress in rats. Male Wistar rats (weighing 150200 g) received colchicine intracerebroventricularly(15 .g per rat), and cognitive dysfunctions were evaluated by the Morris water maze and the plus maze performance task andsupported by biochemical tests. Central administration of colchicine caused memory deficit in both the Morris water mazeand the elevated plus maze task paradigm tasks. Chronic treatment with curcumin (550 mg/kg, p.o.) twice daily for a periodof 25 days beginning 4 days prior to colchicine injection significantly improved the colchicine-induced cognitive impairment.Biochemically, chronic administration of curcumin significantly reduced the elevated lipid peroxidation, restored the decreasedreduced glutathione level and acetylcholinesterase activity, and attenuated the raised colchicine-induced elevated nitrite lev-els. The results of the present study indicate that curcumin has a protective role against colchicine-induced cognitive impair-ment and associated oxidative stress.

Hydrothermally synthesized Na₂Ti₃O₇ nanotube–V₂O₅ heterostructures with improved visible photocatalytic degradation and hydrogen evolution - Its photocorrosion suppression

Vattikuti, S.V. Prabhakar,Reddy, Police Anil Kumar,NagaJyothi, P.C.,Shim, Jaesool,Byon, Chan Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.740 No.-

<P><B>Abstract</B></P> <P>There is still a need to prepare heterostructure photocatalysts with high activity and recyclability but without using precious metals to reduce the cost of photocatalysts. Thus, a facile and simple method for the synthesis of a Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst via hydrothermal synthesis is reported herein. The chemical composition, morphology, and structural features of the photocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N<SUB>2</SUB> adsorption–desorption specific surface area analysis (BET), and diffuse reflectance absorption (DRS) methods. It was observed that the specific surface area of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst increased with the incorporation of V<SUB>2</SUB>O<SUB>5</SUB>. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst was then used for the removal of rhodamine B (RhB) under simulated solar light irradiation. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst revealed excellent photocatalytic activity and photodegradation kinetics as compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. Furthermore, both the photoactivity and long-term stability of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst were superior to those of the pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. The excellent photocatalytic performance of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst can be ascribed to its high specific surface area (283.71 m<SUP>2</SUP>g<SUP>−1</SUP>), mesoporous structure, highly dispersed V<SUB>2</SUB>O<SUB>5</SUB> nanoparticles, and hindrance of electron–hole pair recombination of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> due to the V<SUB>2</SUB>O<SUB>5</SUB> incorporation, which is proven by the photoelectrochemical results, including photocurrent and electron impendence spectroscopy results. In addition, during the study of photocatalytic hydrogen evolution, the hydrogen yield of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> nanocomposite was 1.83 times that of pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>, which also exhibited excellent photocatalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heterojunction of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs was developed via hydrothermal method. </LI> <LI> Visible photocatalytic RhB degradation studies were performed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> <LI> Improved degradation efficiency was observed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs when compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs. </LI> <LI> V<SUB>2</SUB>O<SUB>5</SUB> NPs were successfully utilized as cocatalyst for pollutant degradation. </LI> <LI> Charge recombination was diminished in the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs by the addition of V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation of molten fuel coolant interaction phenomena using real time X-ray imaging of simulated woods metal-water system

Avinash Kumar Acharya,Anil Kumar Sharma,Ch.S.S.S. Avinash,Sanjay Kumar Das,Lydia Gnanadhas,B.K. Nashine,P. Selvaraj 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.7

In liquid metal fast breeder reactors, postulated failures of the plant protection system may lead toserious unprotected accidental consequences. Unprotected transients are generically categorized astransient overpower accidents and transient under cooling accidents. In both cases, core meltdown mayoccur and this can lead to a molten fuel coolant interaction (MFCI). The understanding of MFCI phenomenais essential for study of debris coolability and characteristics during post-accident heat removal. Sodium is used as coolant in liquid metal fast breeder reactors. Viewing inside sodium at elevatedtemperature is impossible because of its opaqueness. In the present study, a methodology to depict MFCIphenomena using a flat panel detector based imaging system (i.e., real time radiography) is brought outusing a woods metal-water experimental facility which simulates the UO2-Na interaction. The developedimaging system can capture attributes of the MFCI process like jet breakup length, jet front velocity,fragmented particle size, and a profile of the debris bed using digital image processing methods likeimage filtering, segmentation, and edge detection. This paper describes the MFCI process and developedimaging methodology to capture MFCI attributes which are directly related to the safe aspects of a sodiumfast reactor.

Strain mediated magnetoelectric coupling in a NiFe₂O₄–BaTiO₃ multiferroic composite

Gorige, Venkataiah,Kati, Raju,Yoon, D H,Anil Kumar, P S IOP 2016 Journal of Physics. D, Applied Physics Vol.49 No.40

<P>In this paper we demonstrate significant magnetoelectric coupling in ferrimagnetic, NiFe<SUB>2</SUB>O<SUB>4</SUB>, and ferroelectric, BaTiO<SUB>3</SUB>, multiferroic composite bulk materials by measuring temperature dependent magnetization. X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy data show that the two phases coexist with a highly crystalline and sharp interface without any detectable impurities, which enables significant magnetoelectric (ME) coupling. The temperature dependent magnetization data of the composite clearly show the jumps in magnetization curves at the structural phase transitions of BaTiO<SUB>3</SUB>, thereby indicating their origin in ME coupling. The change in coercivity of composite sample in different ferroelectric phases of BaTiO<SUB>3</SUB> has been observed compared to the NiFe<SUB>2</SUB>O<SUB>4</SUB> sample. The different lattice strains corresponding to different ferroelectric phases of BaTiO<SUB>3</SUB> could be the driving force for modulating the magnetization and coercivity of the composite material. This is clear evidence of strain mediated ME coupling in ferrimagnetic and ferroelectric composite materials.</P>

Prevalence of Phytophthora Blight of Pigeonpea in the Deccan Plateau of India

M. Sharma,S. Pande,M. Pathak,J. Narayana Rao,P. Anil Kumar,D. Madhusudan Reddy,V. I. Benagi,D. M. Mahalinga,K. K. Zhote,P. N. Karanjkar,B. S. Eksinghe 한국식물병리학회 2006 Plant Pathology Journal Vol.22 No.4

drechsleri f. sp. cajani is the third potentially important disease of pigeonpea in the Deccan Plateau (DP) of India after wilt and sterility mosaic. In the rainy-season of 2005, an outbreak of PB was seen throughout DP. To quantify the incidence and spread of the disease, a systematic survey was conducted in the major pigeonpea growing regions of DP during the crop season 2005. Attempts were made to determine the effect of cropping systems on the PB development and identify resistant cultivars, if any, grown by farmers and on research farms. Widespread incidence of PB was recorded on improved, and or local cultivars grown in different intercropping systems. Majority of improved cultivars grown at research farms were found susceptible to PB (>10% disease incidence). Pigeonpea intercropped with groundnut, black gram and coriander had less disease incidence (≤10%). Three wilt and SM resistant pigeonpea cultivars KPL 96053, ICPL 99044, and ICPL 93179 were found resistant (<10%) to PB as well. However, their resistance to PB needs confirmation under optimum disease development environments.

Prevalence of Phytophthora Blight of Pigeonpea in the Deccan Plateau of India

Sharma, M.,Pande, S.,Pathak, M.,Rao, J. Narayana,Kumar, P. Anil,Reddy, D. Madhusudan,Benagi, V.I.,Mahalinga, D.M.,Zhote, K.K.,Karanjkar, P.N.,Eksinghe, B.S. The Korean Society of Plant Pathology 2006 Plant Pathology Journal Vol.22 No.4

Phytophthora blight(PB), caused by Phytophthora drechsleri f. sp. cajani is the third potentially important disease of pigeonpea in the Deccan Plateau(DP) of India after wilt and sterility mosaic. In the rainy-season of 2005, an outbreak of PB was seen throughout DP. To quantify the incidence and spread of the disease, a systematic survey was conducted in the major pigeonpea growing regions of DP during the crop season 2005. Attempts were made to determine the effect of cropping systems on the PB development and identify resistant cultivars, if any, grown by farmers and on research farms. Widespread incidence of PB was recorded on improved, and or local cultivars grown in different intercropping systems. Majority of improved cultivars grown at research farms were found susceptible to PB(>10% disease incidence). Pigeonpea intercropped with groundnut, black gram and coriander had less disease incidence(${\leq}10%$). Three wilt and SM resistant pigeonpea cultivars KPL 96053, ICPL 99044, and ICPL 93179 were found resistant(<10%) to PB as well. However, their resistance to PB needs confirmation under optimum disease development environments.

Interplay of Structural Distortions, Dielectric Effects and Magnetic Order in Multiferroic GdMnO3

Mathias Doerr,Michael Loewenhaupt,Aditya A. Wagh,P. S. Anil Kumar,Suja Elizabeth,Sahana Roessler,Martin Rotter,Steffen Wirth 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10

Multiferroic materials are characterized by simultaneous magnetic and ferroelectric ordering making them good candidates for magneto-electrical applications. We conducted thermal expansion and magnetostriction measurements in magnetic fields up to 14 T on perovskitic GdMnO3 by highresolution capacitive dilatometry in an effort to determine all longitudinal and transversal components of the magnetostriction tensor. Below the ordering temperature TN = 42 K, i.e., within the different complex (incommensurate or complex) antiferromagnetic phases, lattice distortions of up to 100 ppm have been found. Although no change of the lattice symmetry occurs, the measurements reveal strong magneto-structural phenomena, especially in the incommensurate sinusoidal antiferromagnetic phase. A strong anisotropy of the magnetoelastic properties was found, in good agreement with the type and propagation vector of the magnetic structure. We demonstrate that our capacitive dilatometry can detect lattice expansion effects and changes of the dielectric permittivity simultaneously because the sample is housed inside the capacitor. A separation of both effects is possible by shielding the sample. Dielectric transitions could be detected by this method and compared to the critical values of H and T in the magnetic phase diagram. Dielectric changes measured at 1 kHz excitation frequency are detected in GdMnO3 at about 180 K,and between 10 K and 25 K in the canted antiferromagnetic structure which is characterized by a complex magnetic order on both the Gd- and Mn-sites.

Simple 4-segment thermal cycling pyroelectric measurement protocol for differentiating between ferroelectric and non-ferroelectric materials

Wagh Aditya A.,Bhat Shwetha G.,Anusree V.K.,Santhosh P.N.,Elizabeth Suja,Kumar P.S. Anil 한국물리학회 2023 Current Applied Physics Vol.49 No.-

The rare-earth chromates, RECrO3 and manganites REMnO3 (RE = Eu, Y, Dy, Ho, Gd) are considered potential room temperature multiferroics. However, artefacts and undesirable signals pose a severe challenge in confirming the ferroelectric (FE) phase, especially in pyroelectric current measurement technique. We propose a simple modified approach to the technique, named as 4-segment thermal cycling protocol. This protocol assists in isolating the irreversible thermally stimulated current from those associated with spontaneous and reversible nature of the electric polarization in FE phase. Here, we have compared simulated response of two hypothetical materials; an FE material and a paraelectric material. Further, we experimentally verify the protocol in a single crystal of prototype FE material, Glycine Phosphite. Using the proposed protocol, we investigated polycrystalline materials, HoCrO3 (reported multiferroic earlier) and DyFe0.5Mn0.5O3. Our results expound on the absence of reversible spontaneous electric polarization in temperature ranges tested.