Antiferromagnetism in NdBa/sub 2/Cu/sub 3/O/sub 6. 1/ Page: 3 of 8
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In Figure(1) we show, at 80K, two sets of scans through the (1/2 1/2 L) magnetic reflec-
tions for both integer and half integer L . The data clearly indicate the presence of strong
(1/2 1/2 1) peaks with L half integer while the intensity at the scattering vectors (1/2 1/2 L) with
integer 1, is barely above bakground. The integer I scattering was carefully monitored over
a wide temperature range. Although there may be weak (1/2 1/2 L integer) fluctuations we
find no evidence for a genuine long range ordered component from 80 to 385 K. In figure(2)
we show the temperature variation of the integrated intensity of the (1/2 1/2 3/2) magnetic
reflection. As T is increased up to TN = 385K, the intensity vanishes continuously.
In Table I we give a set of integrated intensities of (H/2 H/2 L/2) peaks with H, L odd
integers. These intensities were collected at room temperature using 6/20 scan mode. The
evolution of these measured magnetic structure factors with the L component of the scattering
vector is clearly compatible with spins lying in the tetragonal planes. Assuming collinear spins
with the same magnitude < S > on the CuO2 layers and antiferromagnetic nearest neighbour
ordering of the CuO2 planes, we write the magnetic structure factor as FM -< S > [e+2co(2arlu)J
where I is half integer and a is the fraction of magnetization lying in the oxygen deficient
planes; u is the z coordinate of the CuO2 plane in units of c. We used a and < s > as two
adjustable parameters to fit the observed magnetic intensities of 10 reflections listed in Table
I. Making use of the magnetic form factor f(Q) of the Cu2+ ions determined experimentally
in La2CuO4 by Freltoft et al ,. we obtained the best fit of our data for the positive value of
e = 0.10 0.02 and the ordered moment on the CuO2 planes of < s >= 0.40 0.02. For these
values the calculated intensities are reported in Table I as well as the corresponding results
for the case where no staggered magnetization is present in the oxygen deficient layers. In this
fit u was fixed equal to the value 0.355 f 0.002 which we determined on the same sample using
structural refinement of 20 independent nuclear reflections. The resulting magnetic structure
consists of alternating 3 spins(+) and 3 spins(-) along the tetragonal direction. Surprisingly,
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Moudden, A.H.; Shirane, G.; Tranquada, J.M.; Birgeneau, R.J.; Endoh, Y.; Yamada, K. et al. Antiferromagnetism in NdBa/sub 2/Cu/sub 3/O/sub 6. 1/, article, January 1, 1988; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc1197708/m1/3/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.