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Dive into the research topics where P. Molho is active.

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Featured researches published by P. Molho.


Journal of Magnetism and Magnetic Materials | 1980

Onset of magnetism in the yttrium-nickel compounds: II. Very weak itinerant ferromagnetism in YNi3

D. Gignoux; R. Lemaire; P. Molho; F. Tasset

Abstract Whereas YNi 5 is a Pauli paramagnet a resurgence of magnetism occurs for larger amounts of Y, as observed in Y 2 Ni 7 and YNi 3 . From a macroscopic point of view, YNi 3 is a very weak itinerant ferromagnet which behaves as ZrZn 2 . Polarized neutron diffraction experiments on a YNi 3 single crystal have shown that the resurgence was not due to the yttrium 4d electrons, but to the nickel 3d electrons, the spatial distribution of which is analogous to that observed in nickel metal. The resurgence of magnetism and its localization are discussed in terms of the band structure of the alloy.


Journal of Magnetism and Magnetic Materials | 1980

Onset of magnetism in the yttrium-nickel compounds: I. Collective electron metamagnetism in Y2Ni17

D. Gignoux; R. Lemaire; P. Molho

Abstract In the homogeneity range of the Y 2 Ni 17 phase the compounds are weak ferromagnets. Some Ni atoms are ferromagnetic, others for which the Stoner criterion is almost fulfilled show metamagnetism of collective electrons. This property, previously observed in ThCo 5 , manifests itself in Y 2 Ni 16 with a maximum in the thermal variations of the spontaneous magnetization and of the superposed susceptibility. At low temperature a transition to a state of higher magnetization is observed in high fields. Differences in the local Ni environment are important. Small variations of the composition can induce modifications of the magnetic interactions large enough to stabilize low or high magnetization states.


Journal of Applied Physics | 1987

Irreversible evolution in the topology of magnetic domains (invited)

P. Molho; J.L. Porteseil; Y. Souche; J. Gouzerh; J. C. S. Levy

Hysteresis does not vanish in materials essentially free from defects and domain wall pinning. It arises from the existence of many geometrically different domain structures separated by intrinsic energy barriers. Although generally metastable, these states can nevertheless be explored by suitable excursion in the manifold of domain structures, along which irreducible irreversibility is present. This idea is illustrated by experiments performed on garnet layers with uniaxial anisotropy (bubble material). Cooling the layer from T>Tc in a field H normal to it results in various states: parallel stripes (H=0), bubbles of increasing diameters and mixtures of bubbles and stripes (H<52 Oe), and mazes of convoluted stripes with defects (forks, dead ends). Cycling the applied field at constant temperature also causes evolution of the structure. For example, starting from parallel stripes the structure evolves toward a maze with intermediate steps corresponding to stripe folding, and then there is the onset of def...


Journal of Applied Physics | 1981

New properties associated with the occurrence of d‐band magnetism in the Y‐Ni compounds

D. Gignoux; R. Lemaire; P. Molho; F. Tasset

Among the Y‐Ni compounds, four different behaviours, characteristic of the occurrence of d ferromagnetism in intermetallics have been observed : Exchange Enhanced Pauli Paramagnetism in YNi5 and YNi2, Very Weak Itinerant Ferromagnetism in YNi3, Collective Electron Metamagnetism in Y2Ni17 and Thermal Spontaneous Magnetization in Y2Ni7. The evolution of the magnetic properties as a function of the yttrium concentration is discussed in the light of the band structure of the different compounds.


Journal of Magnetism and Magnetic Materials | 1986

Topological hysteresis in stripe domain structures

P. Molho; J. Gouzerh; J.C.S. Levy; J.L. Porteseil

Abstract Irreversible evolution in stripe domain structures in a bubble material was investigated. Equilibrium parallel stripe structure folds progressively up to the labyrinth one under normal magnetic field cycles. This topological hysteresis, not related to wall-pinning by defects but to nucleation and collapse field problems, shows memory effects of upper fields encountered.


Journal of Magnetism and Magnetic Materials | 1990

“Thermal spontaneous magnetization” in Y2Ni7: A misinterpretation

R. Ballou; B. Gorges; P. Molho; P. Rouault

Abstract The previous suggestion about the occurence of a thermally induced ferromagnetism in the intermetallic compound Y 2 Ni 7 appears now as a misinterpretation of the experimental results. The observed behaviour originates actually from the existence of gadolinium impurities in the studied sample and is interpreted in terms of an inhomogeneous ferrimagnetism.


Journal of Magnetism and Magnetic Materials | 1983

Magnetic hysteresis near the Curie temperature of Gd

P. Molho; J.L. Porteseil

Abstract We measured the temperature dependences of H c , M R and of Barkhausen noise power on a Gd polycrystal. We observed a crossover from Bloch to Ising-type walls and a decrease of the domain size near T c . The magnetizations acquired by alternating and thermal demagnetizations under a bias field were compared.


Journal of Magnetism and Magnetic Materials | 2001

Hysteresis near the compensation of a ferrimagnetic garnet film

P. Molho; M.P de Albuquerque

Abstract Magnetization measurements and observations using Faraday effect were performed on a ferrimagnetic garnet film, around the compensation temperature ( T comp ). Besides the large increase of the domains size close to T comp , field cycles at different temperatures and thermal variations at different fields show the evolution between metastable states: domains, up or down saturated states and ‘spin-flop’ states very close to T comp .


Journal of Magnetism and Magnetic Materials | 1993

Patterns in a ferrofluid film under normal fields: shape of thickness modulations and hysteresis

P.A. Petit; M.P. de Albuquerque; V. Cabuil; P. Molho

Abstract A film of ferrofluid, subjected to normal fields, shows thickness modulations that appear as lattices of ‘bubbles’. Depending on field variations and magnetic history, different patterns and hysteresis are obtained. Using image processing, some of these patterns have been analyzed and the shape of thickness modulations measured to deduce the evolution of surface and gravity energy terms.


Journal of Magnetism and Magnetic Materials | 1992

Evolution of the domain-like pattern in a film of ferrofluid in normal fields

P.A. Petit; M.P. de Albuquerque; V. Cabuil; P. Molho

Abstract A film of ferrofluid, standing on a non-magnetic fluid of higher density and subjected to a normal field, shows thickness modulations, organized in a hexagonal lattice, which are analogous to the domain structure in magnetic bubble materials. The period of the lattice is a function of the magnetic field, and when the field varies, the pattern evolves between different metastable states and with hytereis. We study experimentally the patterns obtained when, starting from a hexagonal lattice under field H1, the field is increased to H2, for different values of H2. The resulting patterns are inhomogenous, with small bubbles surrounding the large ones characteristic of the initial lattice. We develop a phenomenological model which relates the number of small bubbles by unit cell to the ratio between the periods of the homogeneous states corresponding to the initial and final fields.

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R. Ballou

Centre national de la recherche scientifique

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J.L. Porteseil

Centre national de la recherche scientifique

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D. Gignoux

Centre national de la recherche scientifique

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M.P. de Albuquerque

Centre national de la recherche scientifique

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R. Lemaire

Centre national de la recherche scientifique

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Vasile Heresanu

Centre national de la recherche scientifique

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E. Olive

Centre national de la recherche scientifique

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J. Gouzerh

Centre national de la recherche scientifique

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P.A. Petit

Centre national de la recherche scientifique

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Y. Souche

Centre national de la recherche scientifique

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