scispace - formally typeset
Search or ask a question
Author

V. R. K. Murthy

Bio: V. R. K. Murthy is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Dielectric & Rietveld refinement. The author has an hindex of 27, co-authored 162 publications receiving 2595 citations. Previous affiliations of V. R. K. Murthy include VIT University & Indian Institute of Science.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, X-ray diffraction has been used to confirm the presence of two phases of magnetorrolectric phase transition in composite materials, which is explained in the light of structural phase transition.
Abstract: Composites with composition xBa08Pb02TiO3+ (1 −x) Ni093Co002Mn005Fe195O4-δ in which x varies as 10, 09, 07 and 05 in molar percent have been prepared by the conventional ceramic double sintering process The presence of the two phases has been confirmed by X-ray diffraction These composites were prepared for their use as magnetoferrolectric devices Variation of longitudinal modulus (L) and internal friction loss (Q −1) of these samples with temperature at 142 kHz has been studied in the wide temperature range 300 to 630 K The elastic behaviour (L) showed a break at the ferroelectric Curie temperature (498 K) in the case of pure ferroelectric material (Ba08Pb02TiO3) This break shifted to lower temperature side as the ferrite component increases in the composite The temperature variation of internal friction loss (Q −1) showed a corresponding stress induced relaxation peak at the ferroelectric-non-ferroelectric phase transition This behaviour is explained in the light of structural phase transition

22 citations

Journal ArticleDOI
TL;DR: In this article, a new ferromagnetic-dielectric particulate composites of Ni 0.5Zn 0.52Ti 0.48O 3 (PZT) and PbZr 0.95O 4−δ δ (NZF) were prepared by conventional ceramic method, and detailed studies on the dielectric properties were done confirming that the magnetoelectric interaction between the constituent phases may result in various anomalies in the composites.
Abstract: Novel ferromagnetic-dielectric particulate composites of Ni 0.5Zn 0.5Fe 1.95O 4−δ (NZF) and PbZr 0.52Ti 0.48O 3 (PZT) were prepared by conventional ceramic method. The presence of two phases in composites was confirmed by XRD technique. The variations of dielectric constant ( 𝜀 ) with frequency in the range of 100 kHz–1 MHz at room temperature and also with temperature at three different frequencies (50 kHz, 100 kHz, and 500 kHz) were studied. Detailed studies on the dielectric properties were done confirming that the magnetoelectric interaction between the constituent phases may result in various anomalies in the dielectric behaviour of the composites. It is proposed that interfaces play an important role in the dielectric properties, causing space charge effects and Maxwell-Wagner relaxation, particularly at low frequencies and high temperatures. The piezoelectric d33 constant was studied at room temperature, and the d33 constant value decreased with ferrite content. Magnetic properties like B-H loops traces were studied to understand the saturation magnetic ( Ms) and magnetic moment ( 𝜇 𝐵 ) of the present particulate composites. The magnetoelectric (ME) output was measured by varying dc bias magnetic field. A large ME output signal of 2780 mV/cm Oe was observed in the composite having 50% ferrite. The temperature variation of longitudinal modulus ( L) and internal friction ( Q−1) of these particulate composites at 104 kHz was studied in the temperature range 30°C–420°C by the composite oscillator technique. Longitudinal modulus showed a sharp minimum, and internal friction exhibits a sharp peak at ferroelectric-paraelectric phase transition. These ferroelectric-dielectric particulate composites were prepared with a view to using them as ME sensors and transducers.

22 citations

Journal ArticleDOI
TL;DR: In this article, the coefficient of volume expansion of the alkyl-cyano-biphenyl liquid crystal CnH2n+1C6H4C 6H44.
Abstract: Dilatometric studies were performed on the nematic and isotropic phases of the homologous series of alkyl-cyano-biphenyl liquid crystals CnH2n+1C6H4C6H4. CN for n = 5 to 9. From these studies the coefficient of volume expansion (a) of the liquid crystal is estimated. Using this data a number of thermoacoustic and an harmonic parameters of the liquid crystal are evaluated. The temperature dependence of these parameters have also been investigated. All these thermoacoustic and an harmonic parameters evaluated in this case show characteristic change in the immediate vicinity of the phase transition temperature.

22 citations

Journal ArticleDOI
TL;DR: In this article, the dependence of microwave dielectric properties on the structural characteristics of BaA2Ti3O10 (A ǫ, Nd and Sm) was investigated.

22 citations

Journal ArticleDOI
TL;DR: In this article, the effect of external applied stress on the open magnetic circuit type coil with these ferrites was studied by applying uniaxial compressive stress parallel to the magnetising direction and the change in the inductance was measured.

21 citations


Cited by
More filters
Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Proceedings Article
01 Jan 1999
TL;DR: In this paper, the authors describe photonic crystals as the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures, and the interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

2,722 citations

01 Sep 1955
TL;DR: In this paper, the authors restrict their attention to the ferrites and a few other closely related materials, which are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present.
Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

2,659 citations

Journal ArticleDOI
TL;DR: In this article, a 3d transition metal-doped ZnO films (n-type Zn1−xMxO) were formed on sapphire substrates using a pulsed-laser deposition technique, and their magnetic and electric properties were examined.
Abstract: 3d-transition-metal-doped ZnO films (n-type Zn1−xMxO (x=005–025): M=Co, Mn, Cr, Ni) are formed on sapphire substrates using a pulsed-laser deposition technique, and their magnetic and electric properties are examined The Co-doped ZnO films showed the maximum solubility limit Some of the Co-doped ZnO films exhibit ferromagnetic behaviors with the Curie temperature higher than room temperature The magnetic properties of Co-doped ZnO films depend on the concentration of Co ions and carriers

1,852 citations

Journal ArticleDOI
TL;DR: In this paper, a review focusing on promising candidate materials (such as GaN, GaP and ZnO) is presented, where the introduction of Mn into these and other materials under the right conditions is found to produce ferromagnetism near or above room temperature.
Abstract: Recent advances in the theory and experimental realization of ferromagnetic semiconductors give hope that a new generation of microelectronic devices based on the spin degree of freedom of the electron can be developed. This review focuses primarily on promising candidate materials (such as GaN, GaP and ZnO) in which there is already a technology base and a fairly good understanding of the basic electrical and optical properties. The introduction of Mn into these and other materials under the right conditions is found to produce ferromagnetism near or above room temperature. There are a number of other potential dopant ions that could be employed (such as Fe, Ni, Co, Cr) as suggested by theory [see, for example, Sato and Katayama-Yoshida, Jpn. J. Appl. Phys., Part 2 39, L555 (2000)]. Growth of these ferromagnetic materials by thin film techniques, such as molecular beam epitaxy or pulsed laser deposition, provides excellent control of the dopant concentration and the ability to grow single-phase layers. T...

968 citations