Search results for: A.K. Nigam

Items from 1 to 20 out of 120 results

article

γ-Fe2WO6 – A magnetodielectric with disordered magnetic and electronic ground states

Soumendra Nath Panja, Jitender Kumar, Luminita Harnagea, A.K. Nigam, more

Journal of Magnetism and Magnetic Materials > 2018 > 466 > C > 354-358

The magnetic, thermodynamic and dielectric properties of the γ-Fe₂WO₆ system is reported. Crystallizing in the centrosymmetric Pbcn space group, this particular polymorph exhibits a number of different magnetic transitions, all of which are seen to exhibit a finite magneto-dielectric coupling. At the lowest measured temperatures, the magnetic ground state appears to be glass-like, as evidenced by...

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Evidence for reentrant spin glass behavior in transition metal substituted Co-Ga alloys near critical concentration

Sk. Mohammad Yasin, V. Srinivas, S. Kasiviswanathan, Megha Vagadia, more

Journal of Magnetism and Magnetic Materials > 2018 > 451 > C > 327-335

In the present study magnetic and electrical transport properties of transition metal substituted Co-Ga alloys (near critical cobalt concentration) have been investigated. Analysis of temperature and field dependence of dc magnetization and ac susceptibility (ACS) data suggests an evidence of reentrant spin glass (RSG) phase in Co_55.5TM₃Ga_41.5 (TM = Co, Cr, Fe, Cu). The magnetic transition temperatures...

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Influence of Mn-substitution on the magnetic and thermal properties of TbCrO3

Megha Vagadia, S. Rayaprol, A.K. Nigam

Journal of Alloys and Compounds > 2018 > 735 > C > 1031-1040

Studies on the Mn-substitution induced modification in the structural, thermal, magnetic and magnetocaloric properties of TbCrO₃ orthochromite are presented. The phase formation and purity of the samples were examined by analyzing X-ray diffraction (XRD) patterns. Magnetization measurements as a function of temperature reveal the antiferromagnetic ordering of Cr³⁺ spins (T_N1) at ∼ 157 K and Tb³⁺ spins...

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Metamagnetism-enhanced magnetocaloric effect in the rare earth intermetallic compound Ho5Ge4

R. Nirmala, A.V. Morozkin, R. Rajivgandhi, A.K. Nigam, more

Journal of Magnetism and Magnetic Materials > 2016 > 418 > C > 118-121

Magnetic and magnetocaloric properties of polycrystalline Ho₅Ge₄ (orthorhombic, Sm₅Ge₄-type, Space group Pnma, No. 62, oP36) compound have been studied. This compound orders antiferromagnetically at ~24K (T_N). From the magnetization vs field isotherms obtained close to the magnetic transition temperature, magnetocaloric effect (MCE) has been estimated. The isothermal magnetic entropy change (ΔS_M)...

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Evolution of ferromagnetic interactions from cluster spin glass state in Co–Ga alloy

Sk. Mohammad Yasin, Ritwik Saha, V. Srinivas, S. Kasiviswanathan, more

Journal of Magnetism and Magnetic Materials > 2016 > 418 > C > 158-162

Low temperature magnetic properties of binary Co_xGa_100−x (x=54–57) alloy have been investigated. Analysis of frequency dependence of ac susceptibility provided a conclusive evidence for the existence of cluster spin glass like behavior with the freezing temperature ~8, 14K for x=54, 55.5 respectively. The parameters for conventional ‘slowing down’ of the spin dynamics have been extracted from the...

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Effect of microstructure and texture on the magnetic and magnetocaloric properties of the melt-spun rare earth intermetallic compound DyNi

R. Rajivgandhi, J. Arout Chelvane, A.K. Nigam, Je-Geun Park, more

Journal of Magnetism and Magnetic Materials > 2016 > 418 > C > 9-13

Magnetization measurements have been carried out on the melt-spun ribbon sample of the rare earth intermetallic compound DyNi (Orthorhombic, FeB-type, Space group Pnma) and its magnetic and magnetocaloric properties are compared with those of the arc-melted analog. The arc-melted DyNi orders ferromagnetically at around 61K (T_C) whereas the melt-spun DyNi orders ferromagnetically at about 47K. The...

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Magnetic and electrical studies of Ho0.9RE0.1CrO3 (RE=Gd and Yb) multiferroics

Shubhra Mathur, Anjali Krishnamurthy, A.K. Nigam

Perspectives in Science > 2016 > 8 > C > 72-75

We report magnetic and electrical studies on multiferroic systems Ho_0.9(RE)_0.1CrO₃ where RE symbolizes rare earths like Gd and Yb. Solid state diffusion method has been used to synthesize the samples. Structural phase formation has been confirmed with the help of powder X-ray diffraction. Magnetization measurements show canted antiferromagnetic nature with a weak ferromagnetic phase. Néel temperature...

article

Magnetic order of Y3NiSi3-type R3NiSi3 (R=Gd–DY) compounds

A.V. Morozkin, V.O. Yapaskurt, R. Nirmala, S.K. Malik, more

Journal of Magnetism and Magnetic Materials > 2016 > 398 > C > 141-147

Magnetic measurements and neutron powder diffraction investigations on the Y₃NiSi₃-type R₃NiSi₃ compounds (R=Gd, Tb, Dy) reveal their complex antiferromagnetic ordering. Magnetic measurements on Gd₃NiSi₃, Tb₃NiSi₃ and Dy₃NiSi₃ indicate antiferromagnetic-like transition at temperatures 260K, 202K and 140K, respectively. Also, the Tb₃NiSi₃ and Dy₃NiSi₃ compounds show spin-reorientation transition at...

article

CoRuFeX (X=Si and Ge) Heusler alloys: High TC materials for spintronic applications

Lakhan Bainsla, M. Manivel Raja, A.K. Nigam, K.G. Suresh

Journal of Alloys and Compounds > 2015 > 651 > C > 631-635

In this paper, CoRuFeX (X = Si, Ge) alloys were investigated by means of x-ray diffraction, Mössbauer spectroscopy, magnetic and magneto-transport measurements. Alloys are found to be exist in Y-type structure with presence of some B2 disorder. High values of Curie temperature (T_C) of 867 K and 833 K are obtained for CoRuFeSi and CoRuFeGe alloys, respectively. The obtained T_C values are found to be...

article

High spin polarization and spin splitting in equiatomic quaternary CoFeCrAl Heusler alloy

Lakhan Bainsla, A.I. Mallick, A.A. Coelho, A.K. Nigam, more

Journal of Magnetism and Magnetic Materials > 2015 > 394 > C > 82-86

In this paper, we investigate CoFeCrAl alloy by means of ab-initio electronic structure calculations and various experimental techniques. The alloy is found to exist in the B2-type cubic Heusler structure, which is very similar to Y-type (or LiMgPdSn prototype) structure with space group F-43m (#216). Saturation magnetization (M_S) of about 2µ_B/f.u. is observed at 8K under ambient pressure, which is...

article

Spin correlations and magnetic order in Co-Ga alloys: A comprehensive study

Sk Mohammad Yasin, Ritwik Saha, V. Srinivas, S. Kasiviswanathan, more

Journal of Alloys and Compounds > 2015 > 649 > C > 1011-1018

Low temperature magnetic properties of binary Co_xGa_100−x alloy with Co concentration in the range 54 ≤ x ≤ 61.5 at% have been investigated. From the temperature and magnetic field dependent magnetization measurements magnetic phase diagram has been identified. Cluster spin glass like features are noticed in x = 54, 55 compositions, while the compositions x > 57 exhibit double magnetic transition...

article

Electrical and magnetic properties of Y-doped La0.5Sr0.5MnO3 manganite system: Observation of step-like magnetization

Subhrangsu Taran, C.P. Sun, C.L. Huang, H.D. Yang, more

Journal of Alloys and Compounds > 2015 > 644 > C > 363-370

The magnetic and transport properties of bulk doped manganite, La_0.5−_yY_ySr_0.5MnO₃ have been studied as a function of (Y) yttrium doping, y, for 0⩽y⩽0.25. In the absence of the yttrium this is a well studied half-doped manganite which is a metallic ferromagnet. With successive doping of Y the system undergoes a transformation from rhombohedral (space group R3¯-C) to orthorhombically (space group Pnma)...

article

Magnetism in RRhGe (R=Tb, Dy, Er, Tm): An experimental and theoretical study

Sachin Gupta, K.G. Suresh, A.K. Nigam, A.V. Lukoyanov

Journal of Alloys and Compounds > 2015 > 640 > C > 56-63

RRhGe (R=Tb, Dy, Er, Tm) compounds have been studied by different experimental probes and theoretical ab initio calculations. These compounds show very interesting magnetic and transport properties. All the compounds are antiferromagnetic with some of them showing spin-reorientation transition at low temperatures. The magnetocaloric effect estimated from magnetization data shows high values in all...

article

Role of ion beam excitations on quasi one-dimensional magnetic system of Mn-doped LiCuVO4

Abhishek Kumar, G.D. Dwivedi, Shiv Kumar, P. Shahi, more

Materials Chemistry and Physics > 2015 > 161 > Complete > 19-25

Induction of short range ferromagnetic ordering has been observed in the quasi one dimensional antiferromagnetic LiCuVO ₄ system with doping of Mn in the octahedral (Cu) site. Though, magnetic ordering is not stable enough as further increase of Mn-concentration, magnetic ordering gets deteriorated. This might be the case that Mn ²⁺ ions, with strong magnetic moment as compared to...

article

Probing exotic magnetic phases and electrical transport in Cr-rich γ-NiFeCr alloys

Pampa Pal, A.K. Majumdar, A.K. Nigam

Journal of Magnetism and Magnetic Materials > 2015 > 381 > Complete > 297-309

We have identified ferromagnetic, antiferromagnetic, and re-entrant spin-glass-like phases in Cr-rich γ-NiFeCr alloys and studied their critical magnetic behavior. Their electrical resistivity exhibits distinct minima between 10 and 24K with ρ∞−√T due to electron–electron interaction effects. Electron–phonon and electron–magnon contributions to ρ are isolated. The magnetoresistance shows hysteresis...

article

Magnetic, thermal and transport behavior in single crystalline RCu2Ge2 (R=La, Ce, Pr and Sm) compounds

H. Mendpara, Devang A. Joshi, A.K. Nigam, A. Thamizhavel

Journal of Magnetism and Magnetic Materials > 2015 > 377 > C > 325-333

Magnetic behavior of single crystalline RCu₂Ge₂ (R=La, Ce, Pr and Sm) compounds is reported. Single crystals were grown using Cu–Ge flux. The compounds crystallize in a tetragonal structure with space group I4/mmm. LaCu₂Ge₂ shows a diamagnetic behavior. CeCu₂Ge₂, PrCu₂Ge₂ and SmCu₂Ge₂ orders antiferromagnetically at ≈4.2, 15 and 14.5K respectively with [001] as the easy axis of magnetization. CeCu...

article

Magnetic couplings in CoFe2O4/FeCo–FeO core–shell nanoparticles

J.M. Soares, O.L.A. Conceição, F.L.A. Machado, A. Prakash, more

Journal of Magnetism and Magnetic Materials > 2015 > 374 > C > 192-196

CoFe₂O₄/FeCo–FeO core–shell nanoparticles with an average particle size of about 4.3nm were prepared by reducing nanoparticles of superparamagnetic cobalt-ferrite under hydrogen and oxygen atmospheres. The low temperature magnetic hysteresis showed an interesting behavior which has only been observed in thin film multilayer systems. At low magnetic fields H(<0.2kOe) the behavior is dominated by...

article

The nature of the first order isostructural transition in GdRhSn

Sachin Gupta, K.G. Suresh, A.K. Nigam, Y. Mudryk, more

Journal of Alloys and Compounds > 2014 > 613 > Complete > 280-287

We present structural, magnetic, thermal, magnetocaloric, and electrical transport properties of polycrystalline GdRhSn. Magnetization data show that it orders antiferromagnetically at T _N =16.2K. The compound has the ZrNiAl type hexagonal crystal structure at room temperature and undergoes a first order iso-structural transition in the paramagnetic state at 245K. The unit cell volume change...

article

Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

Lakshman Dhal, Chattarpal, R. Nirmala, P.N. Santhosh, more

Physica B: Condensed Matter > 2014 > 448 > C > 300-303

Polycrystalline Gd_0.15Ca_0.85MnO₃ sample was prepared by solid state reaction method and nanocrystalline samples of different grain sizes of the same were prepared by sol–gel method. Phase purity and composition were verified by room temperature X-ray diffraction and SEM-EDAX analysis. Magnetization data of bulk Gd_0.15Ca_0.85MnO₃ in 5kOe field shows a peak at ~119K (T_N) suggesting an antiferromagnetic...

article

Magnetic and magnetocaloric properties of rare earth intermetallic compounds HoCo2−xNix (x=0.75 and 1.25)

Rajib Mondal, R. Nirmala, J. Arout Chelvane, A.K. Nigam

Physica B: Condensed Matter > 2014 > 448 > C > 9-12

Magnetic and magnetocaloric properties of polycrystalline rare earth intermetallic compounds HoCo_2−xNi_x (x=0.75 and 1.25) have been investigated. Both HoCo_1.25Ni_0.75 and HoCo_0.75Ni_1.25 compounds crystallize in MgCu₂ type, cubic Laves phase structure (space group Fd3¯m, no. 227) and order ferromagnetically at ~40K and ~36K (T_C) respectively. Field dependent magnetization at 5K shows soft ferromagnetic...

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Search results for: A.K. Nigam

γ-Fe2WO6 – A magnetodielectric with disordered magnetic and electronic ground states

Evidence for reentrant spin glass behavior in transition metal substituted Co-Ga alloys near critical concentration

Influence of Mn-substitution on the magnetic and thermal properties of TbCrO3

Metamagnetism-enhanced magnetocaloric effect in the rare earth intermetallic compound Ho5Ge4

Evolution of ferromagnetic interactions from cluster spin glass state in Co–Ga alloy

Effect of microstructure and texture on the magnetic and magnetocaloric properties of the melt-spun rare earth intermetallic compound DyNi

Magnetic and electrical studies of Ho0.9RE0.1CrO3 (RE=Gd and Yb) multiferroics

Magnetic order of Y3NiSi3-type R3NiSi3 (R=Gd–DY) compounds

CoRuFeX (X=Si and Ge) Heusler alloys: High TC materials for spintronic applications

High spin polarization and spin splitting in equiatomic quaternary CoFeCrAl Heusler alloy

Spin correlations and magnetic order in Co-Ga alloys: A comprehensive study

Electrical and magnetic properties of Y-doped La0.5Sr0.5MnO3 manganite system: Observation of step-like magnetization

Magnetism in RRhGe (R=Tb, Dy, Er, Tm): An experimental and theoretical study

Role of ion beam excitations on quasi one-dimensional magnetic system of Mn-doped LiCuVO4

Probing exotic magnetic phases and electrical transport in Cr-rich γ-NiFeCr alloys

Magnetic, thermal and transport behavior in single crystalline RCu2Ge2 (R=La, Ce, Pr and Sm) compounds

Magnetic couplings in CoFe2O4/FeCo–FeO core–shell nanoparticles

The nature of the first order isostructural transition in GdRhSn

Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

Magnetic and magnetocaloric properties of rare earth intermetallic compounds HoCo2−xNix (x=0.75 and 1.25)

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