Paramagnetic resonance of Gd3+ in yttrium ethyl sulphate single crystals

Solid State Communications,

873—874, 1969.

Vol.7, pp.

Pergamon Press.

Printed in Great Britain

PARAMAGNETIC RESONANCE OF Gd3~ IN YTTRIUM ETHYL SULPHATE SINGLE CRYSTALS P. Wysling Physik.—Institut der Universität Zu.rich, Zurich, Switzerland

(Received 26 March 1969 by J.L. Olsen)

The paramagnetic resonance of Gd3+ has been observed in single crystals of yttrium ethyl sulphate at several temperatures and the spin-Hamiltonian parameters have been determined. The results are compared with those found earlier in the isomorphic lanthanum ethyl sulphate.

SINCE the degeneracy of an S-state ion in a crystal field is removed by higher order per-

BP 3 must vanish in the symmetries CBh or D 6 3h. The remaining coefficients B~are deter-

turbation involving both the crystal field and the spin-orbit coupling, it is informative to consider this ion both in a crystal where it replaces a smaller ion, and in a crystal where it it replaces a larger one. Electron spin resonance 3~incorporated in trigonal measurements of Gd structures reported previously, have been per-

mined by the experiment and for convenience they are usually related to another set of coefficients b in the following way: B~°= 3~b°2 , B4° = 60’ b°4 , B ~ = 12601 b°5. The eigenvalues to first order for H Z are given in reference 5. Between 4.2 °K and 293 °K the line widths of the allowed seven AM = ±1 transitions are independent of temperature. For a Gd concentration of about

formed only with crystals in which Gd3* substitutes for a trivalent ion the radius of which is larger than that of the Gd3~ion. In the present work the system Gd3: Y(C 2H5 SO4)3. 9H20 is investigated and the results are3~: compared with those in the isomorphic system Gd La(C

0.005 they amount to 12G. The hyperfine structure was observed in the central line but it was poorly resolved.

2H5S04)3. 9H20 reported some years ago. 1-3 The trivalent ion in the ethyl sulphate nonahydrate (ES) occupies a site of D3,, point symmetry due theionic nine radii nearest waters 4 to The are neighbor assumed to of be hydration. 1.02 A for Gd3~,0.93 A for Y3~and 1.15 A

From the experimental data we calculated the spin-Hamiltoriian parameters g, b°2,b~,and b5° which compiled together with the valuess for Gd ~ are LaES in Table 1. The algebraic signs of the spin-Hamiltonian parameters are determined by intensity measurements at 4.2 °K. The g-factors of Gd3~: YES are isotropic within the experimental error. It is apparent that in both systems the coefficient b~ is dominant. Therefore the energy levels appear in the zero-field sequence + ~_, + I + ~ + ~

for La ~ respectively, The ESR spectrum of Gd3~: YES can be fitted by the usual phenomenological spinHamiltonian of the form2 =

g~HS+B

C

0

0P

~2’

(S=7/2)

3r2 +B4P4 + B6 6P~ would give a The possible term B6 negligible contribution. The terms B 3P and 4

2

Furthermore b

2° is strongly temperature dependent. perature but there be a maximal It is however not amust monotonic functionvalue of ternbetween 4.2 °K and room temperature. 873

3~

874

Vol.7, No.12

PARAMAGNETIC RESONANCE OF Gd

Table 1 T

b 2° 4cm_1

(°K) 4.2 YES

b6° (10~cm’)

g

Ref.

—3.8 ±0.3

0.5 ±0.3

1.993 ±0.002

156.5 ±1.0

—3.8 ±0.3

0.5 ±0.3

1.987 ±0.002

154.5 ±1.5

—3.6 ±0.4

0.7 ±0.4

1.987 ±0.010

20

199.8 ±1.0

—3.91 ±0.15

0.53

1.990 ±0.002

1

90

204.7 ±2.0

—3.96 ±0.3

0.63

1.990 ±0.002

2

191

—3.68

0.53

77 293

LaES

(10_ 151.6 ±1.0

1,4° (104cm’)

290

±1

3

Applying quadratic interpolation we estimate that the peak values lie in the temperature

symmetries are indistinguishable on the basis of crystalline field splittings.6 In both crystals b

ranges 130—190 °K and 90—150 °K, for YES and LaES respectively. A similar but less strongly marked temperature dependence of the axial parameter was recently reported 3~: LaCl.5 for the In systems Gd ~ LaBr and Gd these crystals the gadolinium ion occupies a site of C 3h point symmetry (C3h and D3h

reaches a weak maximum below 4.2°K.

2°

Acknowledgements

— I am indebted to Mr. W. F.Berlinger Prof. Waidner for for experimental some comments assistance. and to This work has been supported in part by the

Swiss National Science Foundation.

REFERENCES

Can. J. Phys. 34, 341, (1956)

1.

BUCKMASTER HA.,

2.

BLEANEY B., SCOVIL H.E.D. and TRENAM R.S., Proc. R. Soc. A 223, 15 (1954).

3.

HUTCHISON C.A., Jr., JUDD B.R. and POPE D.F.O., Proc. phys. Soc. B 70, 514 (1957).

4.

KETELAAR J.A.A., Physica 4, 619 (1937).

5.

BOATNER L.A., and ABRAHAM M.M., Phys. Rex’. 163, 213 (1967).

6.

WYBOURNE B.G., Spectroscopic Properties of Rare Earths

John Wiley, New York (1957).

3~ in Einkristallen von Yttrium-Aethylsulphat wurde be ivon verschiedenen Temperature n Die paramagnetische Resonanz Gd beobachtet. Die Parameter des zugeh~rigenSpin-Hamiltonoperators wurden bestimmt und mit jenen verglichen, die man früher im isomorphen Lanthan-Aethylsulphat gemessen hat.