Comments on : Evidence for magnetic organization of high Tc superconductor YBa2Cu3O7 observed by neutron diffraction

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Comments on : Evidence for magnetic organization of high Tc superconductor YBa2Cu3O7 observed by

neutron diffraction

B. Farnoux, R. Kahn, A. Brulet, G. Collin, J.P. Pouget

To cite this version:

B. Farnoux, R. Kahn, A. Brulet, G. Collin, J.P. Pouget. Comments on : Evidence for magnetic

organization of high Tc superconductor YBa2Cu3O7 observed by neutron diffraction. Journal de

Physique, 1987, 48 (12), pp.2041-2041. �10.1051/jphys:0198700480120204100�. �jpa-00210649�

2041

Comments

Evidence for magnetic organization ^of high Tc supercon- ductor YBa2Cu3O7 ^observed by ^neutron diffraction

B. Farnoux, ^R. Kahn, ^A. Brulet, ^{G. Collin+ and J.P.} Pouget+

Laboratoire Léon Brillouin*, ^CEN Saclay,

Gif-sur-Yvette Cedex, ^France

+Laboratoire de Physique ^des Solides, ^Bât. 510, ^UA 02, Université Paris-Sud,

Orsay, ^France

(Regu le

^octobre 1987, accept ^le

^octobre 1987)

In [1]

^{reported the} existence of

lous increase of intensity, ^observed by

powder diffraction, occurring ⁱⁿ

magnetic ^field

below Tc,

^{the 001 nuclear} reflection ring ^of

the superconductor YBa2Cu307. ^Two symmet- ric spots appeared ⁱⁿ

plane ^normal

^the mag- netic field direction. This result

obtained

a

non-compacted powder sample.

In the absence of _any appreciable ^modula-

tion in intensity

^the

^{of the} ring (no ^ap-

parent texturation),

^{suggested that this effect}

could be due

magnetic organization ^within

the sample. However, because of the regular

actor

shut-down,

^could

perform ^further experiments.

Very recently additional

sintered and non-sintered samples, with various oxygen concentrations,

^well

^{the observa-}

tion of other nuclear reflections, reveal that the effect previously reported only

^{for uncon-}

strained powders ^{and is due}

magneto-mecha-

nical orientation of the grains,

consequence of the _very anisotropic magnetic properties ^shown by ^this material below Tc [2].

The apparent reversibility

^{observed in}

the first experiment ^{when the} magnetic ^field

switched off,

^due

disorientation of ^the

grains by the vibrations of

low-temperature

device. In absence of vibrations, ^{the structura-}

tion of the diffraction ring ^induced by ^the mag- netic field remains stable

above Tc.

Finally,

recently ^received

preprint by

J.M. Tranquada et ^al. [3] ^who reproduced

observation of the alignment ^of YBa2Cu30fi par- ticles in

magnetic field, ^{and which} provides

confirmation of

results.

Experiments

^{in progress in order}

^ob-

tain

information concerning ^the

ventional structuration of the diffraction _spec- trum, associated with this magneto-mechanical

effect.

J.

Physique

(1987)

^1987,

Classification

Physics ^Abstracts

74.70L -

References

[1] FARNOUX, ^{B. et} al., ^J. Physique ⁴⁸ (1987)

1623.

[2] MCGUIRE, T.R., DINGER, T.R., FREITAS, P.J., GALLAGHER, W.J., PLASKETT, T.S., SANDSTROM, ^{R.L. and} SHAW, T.M., Phys.

Rev. B 36 (1987) ^4032.

[3] TRANQUADA, J.M., GOLDMAN, A.I., ^MOO- DENBAUGH, A.R., SHIRANE, G., SINHA, S.K., VAKNIN, ^{D. and} LEWANDOWSKI, J.T., preprint.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:0198700480120204100