The structural, magnetic and electrical properties of Ho 0.85Tb0.15Fe2Mnx (x = 0-0.15) have been characterized through X-ray diffraction, Curie temperature and electrical resistivity measurements. All the alloys are found to crystallize in C15-type cubic Laves phase structure. It is observed that the lattice parameter increases with increasing Mn concentration. The Curie temperature is found to decrease with increasing x, which is attributed to the net decrease in the exchange splitting of the spin-up and spin-down bands. All the materials are seen to exhibit metallic behavior with a decrease in the slope of ρ versus T curve near the Curie temperature. The resistivity behavior is explained on the basis of s-d scattering mechanism and electron-phonon interaction. Spin fluctuations have been observed through Curie temperature and resistivity measurements. © 2003 Elsevier B.V. All rights reserved.

S. Kasi Viswanathan

Department Of Physics

G. Markandeyulu

J. Arout Chelvane

Fermi level

Hydrogenation

magnetic anisotropy

Magnetic materials

Magnetic moments

Permanent magnets

transducers

X ray diffraction analysis

Curie temperature

Magnetic interactions

PHASE STRUCTURES

Spin fluctuations

HOLMIUM ALLOYS

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Magnetism and Magnetic Materials

Alloys of Y1∈-∈x Gd x Fe2B y (x = 0, 0.25, 0.5, 0.75 and 1; y = 0, 0.1, 0.15 and 0.2) have been prepared and investigated for structural and magnetic properties. The compounds with x = 0 and 1 are found to form in single phase with C15-type cubic Laves phase structure, while those with x = 0.25, 0.5 and 0.75 are observed to form with small quantities of secondary (Y,Gd)Fe3 phase. The lattice parameters, Curie temperature and the average Fe hyperfine field are found to increase with increasing x. The Gd-Gd and Gd-Fe interactions are attributed to be the main reason for the enhancement of magnetic properties. Boron was found to stabilize the (Y,Gd)Fe2 phase without affecting the magnetic properties. © 2008 Springer Science+Business Media B.V.

Hyperfine Interactions

Magnetic properties and mössbauer studies in Y1-x Gd x Fe2

Magnetic and electrical transport studies have been carried out on Ho 0.85Tb0.15Fe2-[x = 0-2] in the temperature range 5-300 K. The saturation magnetization at 5 K is found to increase with increasing Mn content due to the absence of Mn moments. The temperature variation of magnetization reveals several spin reorientation transitions and these are compared with the ac susceptibility results. Electrical resisitvity reveals the dominance of electron magnon scattering at low temperatures and electron-phonon scattering at high temperatures. © 2006 IEEE.

IEEE Transactions on Magnetics

Effect of Mn on the magnetic and electrical properties of Ho 0.85Tb0.15Fe2

Magnetization and magnetoresistance studies have been carried out on Ho0.85Tb0.15Mn2 and Ho0.85Tb 0.15Fe2. The saturation magnetization of Ho 0.85Tb0.15Mn2 is found to be large compared to Ho0.85Tb0.15Fe2. A large negative magnetoresistance of 27% was observed for Ho0.85Tb 0.15Mn2 around the ordering temperature. In the paramagnetic region, a positive magnetoresistance at lower magnetic fields and negative magnetoresistance is at higher magnetic fields have been observed for Ho0.85Tb0.15Mn2. A positive magnetoresistance of 3.5% with a step-like behavior has been observed for Ho0.85Tb 0.15Fe2 at 5 K. © 2005 Elsevier B.V. All rights reserved.

Physica B: Condensed Matter

Magnetic and electrical properties of Ho0.85Tb 0.15Mn2 and Ho0.85Tb0.15Fe2

In the present article, we report the effect of Mn substitution for Fe on the temperature dependence of magnetization, AC magnetic susceptibility and electrical resistivity of Ho 0.85 Tb 0.15 Fe 2 .The compounds Ho 0.85 Tb 0.15 Fe (2-x) Mnx [x = 0-2] form in single phase with cubic Laves phase structure and the lattice parameter increases with the addition of Mn. The Curie temperature decreases with increasing Mn content due to the reduction in the exchange splitting between the spin up and spin down bands. The magnetization value (at H = 70 kOe) at 5 K is found to increase with increasing Mn concentration. Since the nearest (Mn/Fe)-(Mn/Fe) distances are less than or very close to the critical distance, the Mn atoms do not carry any magnetic moment.

INTERMAG 2006 - IEEE International Magnetics Conference

Magnetoresistance (Δρ ρ) studies have been carried out on the C15-type cubic Laves phase Ho0.85Tb0.15Mn2-xFex (x=0, 0.25, 0.5, 1, and 2) compounds up to a magnetic field of 90kOe at temperatures 5, 30, and 100K. The lattice parameters were found to decrease with increasing x. The Curie temperature is found to increase with increasing x from 30to680K, which is attributed to the net increase in the exchange splitting of the spin-up and spin-down bands. A maximum value of Δρ ρ of -27% was observed for Ho0.85Tb0.15Mn2 around the ordering temperature. This is explained on the basis of nearest Mn-Mn critical distance. A positive magnetoresistance, increasing in a discontinuous manner with increasing field, due to the dependence of scattering of conduction electrons on large magnetoelastic interactions, was observed at 5K in Ho0.85Tb0.15Fe2. © 2005 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Magnetoresistance studies of Ho0.85Tb0.15Mn2-xFex (x=0, 0.25, 0.5, 1, and 2)

The results of low temperature magnetization measurements carried out on the Dy0.73Tb0.27Fe2-xCox system and their hydrogenated compounds are presented. Low temperature (12 K) magnetization data reveals a large increase in anisotropy in the hydrogenated compounds, attributed to a modification in crystalline electric field effects as a result of the orientational ordering of hydrogen atoms in the lattice. The discrete step-wise increase in magnetization upto a field of 2 kOe in the parent alloys and the hydrogenated compounds is attributed to spin-flip metamagnetism. © 1998 Elsevier Science Ltd. All rights reserved.

Solid State Communications

Spin-flip metamagnetism in the laves phase compounds Dy0.73Tb0.27Fe2-xCoxHn

Electrical resistivity studies carried out on (Er1-xPrx)2Fe17 (0.4 ≤ x ≤ 1.0) compounds show that they all possess metallic behaviour in the temperature range 16-400 K. Resistivity at low temperatures shows a T2 dependence, implying that electron-spin wave scattering is dominant in this temperature range. At higher temperatures, the resistivity is due to s-d interaction.

Journal of Alloys and Compounds

Electrical resistivity studies on (Er1-xPrx)2Fe17

Magnetization studies were carried out on the cubic Laves phase Dy0.73Tb0.27Fe2−xNix and Ho0.85Tb0.15Fe2−yNiy [x = y = 0, 0.5, 1.0, 1.5 and 2.0] systems at 4.2 K. These studies indicate that the magnetization process is influenced by the domain wall pinning. The value of the propagation field observed increases with Ni concentration in both the systems up to x = y = 1.5 and falls to a small value for x = y = 2.0. The pinning effect is more pronounced in the case of Dy0.73Tb0.27Fe2−xNix when compared with Ho0.85Tb0.15Fe2−yNiy because of the larger K1 value for Dy0.73Tb0.27Fe2 compared to Ho0.85Tb0.15Fe2. © 1995 IEEE

Observation of domain wail pinning in Dy0.73Tb0.27Fe2-xNix and Ho0.85Tb0.15Fe2-yNiy systems

Alloys of Dy0.73Tb0.27Fe2-xNix [0≤x≤2] were prepared and the lattice parameters obtained at room temperature showed a deviation from Vegard's law owing to the presence of magnetovolume effect. Magnetization studies were carried out up to an applied field of 10 kOe in the temperature range 4.2-750 K. Magnetization data at 4.2 K indicate the effect of domain wall pinning. Temperature dependence of magnetization curves showed maxima at low temperatures as a consequence of this pinning effect. Electrical resistivity studies were carried out in the temperature range 16-750 K. A minimum observed for x=2 in the vicinity of its Curie temperature is attributed to the presence of critical fluctuations due to short-range spin ordering of the rare earths. All the samples, except x=2, showed a T2 dependence at low temperatures and this has been attributed to electron-spin wave scattering mechanism. © 1995 American Institute of Physics.

Fulltext

Journal of Applied Physics

Effect of Ni substitution on the magnetic and electrical properties of Dy0.73Tb0.27Fe2

Cubic Laves phase alloys of Ho0.85Tb0.15Fe 2-xNix (0≤x≤2) were prepared and the lattice parameters, evaluated as a function of x at room temperature, show deviation from Vegard's law. This was attributed to the presence of a magnetovolume effect and charge transfer. Magnetization measurements were performed in the temperature range 77-700 K. The results suggest that the system undergoes a gradual transition from ferri- to ferromagnetic with increasing x. This has been explained based on the 3d band model. Furthermore, a monotonic decrease in Curie temperature with x was observed. Electrical resistivity studies were carried out in the temperature range 16-700 K. An anomaly was found in the vicinity of the Curie temperature for x=2 which has been attributed to the existence of the long-range nature of the critical fluctuations due to short-range spin ordering.

Journal	Data powered by TypesetJournal of Magnetism and Magnetic Materials
Publisher	Data powered by TypesetElsevier
ISSN	03048853
Open Access	No