The influence of A-site disorder on the magnetic and transport properties of Pr0.7-yHoySr0.3MnO3 (y=0, 0.04, 0.08 and 0.1) polycrystalline samples is analyzed within the context of percolative transport and the existence of Griffiths phase. It is seen that the metal-insulator transition temperature is higher than the Curie temperature and coincides with the Griffiths temperature. The percolation threshold was found to increase with the increase in the A-site disorder. © 2004 Elsevier B.V. All rights reserved.

Sankaranarayanan V

Department Of Physics

Mamidanna Sri Ramachandra Rao

Colossal magnetoresistance

Magnetic properties

Magnetic susceptibility

Metal insulator boundaries

Percolation (solid state)

Superconducting transition temperature

GRIFFITHS TEMPERATURE

Manganites

METAL-INSULATOR TRANSITION TEMPERATURE

Transport

Praseodymium compounds

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IIT Madras

Journal of Magnetism and Magnetic Materials

Nanocrystalline [formula omitted] sample has been prepared by sol-gel method. The room temperature powder x-ray diffraction data show single phase nature of the sample and confirm the cubic crystal structure with [formula omitted] space group. The average crystallite size is calculated using Scherrer formula, and it is found to be [formula omitted]. Transmission electron microscopy image shows that the particles are spherical in shape and the average particle size is [formula omitted]. The sample undergoes ferromagnetic ordering at 235 K [formula omitted] and obeys the Curie–Weiss law in the paramagnetic region. The maximum value of the magnetic entropy change [formula omitted] is [formula omitted], and the relative cooling power is [formula omitted] for a field change of 50 kOe. The Arrott plot confirms that the magnetic ordering is of second order nature. The experimentally observed magnetic entropy change of the sample obeys Landau theory of phase transition well. © 2010, American Institute of Physics. All rights reserved.

Fulltext

Journal of Applied Physics

Large magnetic entropy change in nanocrystalline [formula omitted]

The effect of rare earth ion (RE = Er3+, Tb3+, Ho3+) substitution in Pr0.74Sr0.26MnO 3 (PSMO(0.26)) on the magnetic and transport properties is reported. It is found that even for a small concentration of substitution of Pr 3+ ions by Er3+, Tb3+, or Ho3+ ions there is a significant change in the transport and magnetic properties compared to the parent compound Pr0.74Sr0.26MnO3. The observed changes are attributed to the increase in the average A-site disorder upon substituting smaller ions (ionic radius of Er3+ = 1.062 Å, Ho3+ = 1.072 Å, Tb3+ = 1.095 Å) in place of bigger Pr3+ ion (ionic radius = 1.179 Å). The Ho3+ substituted sample was found to behave anomalously when compared to the other two rare earth ion-substituted (Tb3+ and Er3+) samples. Such anomalous behaviour could most likely be caused by the magnetic coupling of the Ho and Mn ions.

European Physical Journal B

Effect of rare earth ion substitution on the magnetic and transport properties of Pr0.7Re0.04Sr0.26MnO3 (RE = Er3+, Tb3+ and Ho3+)

Transport properties of mixed-valence manganites of the type (La0.7-xRx)Ca0.3MnO3 where R = Ho (magnetic) and Y (nonmagnetic) have been investigated above the ferromagnetic transition temperature (Tc). It is interesting to see that the Ho-doped compounds have less resistivity compared to the Y-doped compounds, although Ho and Y ions have almost the same ionic radii and hence lattice strain effect would be the same in both the cases. The internal magnetic field of Ho (μeffHo= 10.5μB) is found to be responsible for this decrease in resistivity in Ho-doped compounds. Coupling of Ho magnetic moment to that of Mn has been confirmed by magnetization measurements. The resistivity data above Tc fit well to the magnetic localization model proposed by Viret et al. [Phys. Rev. B 55, 8067 (1997); Phys. Rev. Lett. 75, 3910 (1995)] and the localization lengths thus obtained are reasonable. The localization lengths of the Ho-doped compounds are greater than that of Y-doped compounds of the same composition indicating that the coupling of the Ho moment with that of the Mn moments is responsible for this effect.

Physical Review B - Condensed Matter and Materials Physics

Magnetotransport studies and mechanism of Ho- and Y-doped La0.7Ca0.3MnO3

Physical Review Letters

Colossal Magnetoresistance is a Griffiths Singularity

Physical Review B

Common features of nanoscale structural correlations in magnetoresistive manganites with a ferromagnetic low-temperature state

Physics Reports

Colossal magnetoresistant materials: the key role of phase separation

Effect of A-site disorder on the percolative transport of Pr (0.7-y)HoySr0.3MnO 3 (y = 0.0, 0.04, 0.08 and 0.1)

Journal	Journal of Magnetism and Magnetic Materials
ISSN	03048853
Open Access	No