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Temperature dependence of 27Al NMR in YAlO3
Volume 91A, number 9
PHYSICS LETTERS
11 October 1982
TEMPERATURE DEPENDENCE OF 27M NMR IN YA1O3 D.P. BURUM, R.M. MACFARLANE, R.M. SHELBY IBM Research Laboratory, 5600 Cottle Rd., San Jose, CA 95193, USA
and L. MUELLER NMR Regional Facility, California Institute of Technology, Pasadena, C’! 91125, USA Received 26 April 1982 Revised manuscript received 15 July 1982 27A1 in yttrium ortho-aluminate has been measured between 30°Cand —150°C.The coupling The nuclear constant quadrupole e2qQ/h varies tensor linearly for from 1.44 to 1.56 MHz over this range, whereas the asymmetry parameter i~drops rapidly from 0.748 toward an asymptotic value of 0.663.
In our application of photon echo nuclear double resonance (PENDOR) to rare-earth ions doped into crystals of YA1O 3 at 2 K we found that we could detect not only the magnetic resonance of the rare-earth nuclei [1], but also the NQR spectra of those aluminum nuclei immediately surrounding the spectra impurity 27Al PENDOR were ions [2]. Since different obtained for different species of rare earth,it was clear that the crystal field was distorted at the nearest
nuclei per unit cell. However, the symmetry of the crystal is such that only two quadrupole multiplets are observed whenever the magnetic field is perpendicular to one of the three orthogonal crystal axes, and these two patterns collapse into a single multiplet when the field the is parallel a crystal axis. Therefore, for simplicity, crystalto axes were chosen as the rotation axes for the experiment. A single crystal of YA1O 3 was used for all the measurements, which were performed at 52.12 MHz. The crystal, which contained some color centers that helped to shorten T1 (the crystal was light brown in color), was shaped into a ~3 mm cube rounded edges and held firmly in a teflon sectionplugs. of 5 mm glass tubing by two The (ID) glass thin tubewalled in turn fit into the goniometer of a variable temperature NMR probe which has been described elsewhere [4]. Spectra such as that shown in fig. 1 were taken 18
neighbor aluminum sites by the substitution of a rare earth ion for an yttrium. In this letter we report on the of an NMR study which we performed on 27Mresults in YAIO 3 over the temperature range 30 to —150°Cin order to determine the27A1 unperturbed 27~ NQR frequenNQR frequencies. The zero field cies at 2 K derived from these NMR results are compared with our PENDOR data elsewhere [2]. Because of the small 27M quadrupole splittings, it was not possible to perform zero field NQR on YA1O 3, and so it was necessary to carry out a full rotation study at high field for each temperature. Yttrium ortho-aluminate has the so-called distorted perovskite structure [3] ~‘ ,with four inequivalent aluminum *
The Geller and Wood [3] definition of the crystal axes is used throughout this letter,
degrees as the crystal was rotated successively about each of its three axes at each of five temperatures, 30, —15, —60, —105 and —150°C.For each spectrum the separation between the central line (m = 1/2 ‘~m = —1/2) and the first satellite (m = 1/2 ~÷m= 3/2) was recorded for each of the two quadrupole multiplets. The result was a set of three curves such as those shown in fig. 2 for each temperature, from which the 465
Volume 91A, number 9
PHYSICS LETTERS
____
r
I
_________
-
(2)
~Ai
(a)
11 October 1982
50
1
/ • •~ ~ •
-
/./
—
YAIO
100
3 T
.
-
150C > -
50
~
U
C
\
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////
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S
•\
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•\
-
.
—
e—
•—s •—•
-60
40
-20
0
20
40
I
60
I
0
Freqeescy Offset (kHz)
Fig. 1. A representative YA1O3 aluminum NMR spectrum. This spectrum was taken at —150°C with the field perpendicular to thea crystal axis. The two five-line quadrupole multiplets corresponding to the two inequivalent aluminum nuclei are indicated. The outermost lines in the spectrum are “folded” since their actual splitting slightly exceeded the sampling bandwidth of the spectrometer (±72kHz).
i
(li)
I
I
50 100 Rotation Angle Ideg.)
200 ~ ~
~ .‘ s-
:— ‘1~
~/
5/
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/
* 1
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LI
. J
00 \
I
\S
C
••/
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2qQ/h, the asymmetry parameter coupling i~and the constant directione cosines giving the orientations of the principal axes of the quadrupole tensor could be determined in the usual manner [5]. These results are presented in table 1, and both e2qQ/h and i~are plotted as functions of temperature in fig. 3. The analysis of the rotation curves was complicated by the high symmetry of the crystal, in that it was not possible to determine unambiguously the signs of the off-diagonal elements of the quadrupole tensor expressed in the crystal axis frame. The eight possibilities fell into two groups of four, each of which represented a set of four tensors for the four aluminum atoms in the unit cell. Within each group of four, the tensors differed only in their orientations. The values presented in table 1 and fig. 3 were chosen both on the basis of comparison with published data on an isostructural compound (GdA1O 3) [6], and because the value of i~resulting from the other possibility took on improbable values (rao.975) and behaved in an unphysical way as a function of temperature. The orientation cosines for one of the four aluminum nuclei in the unit cell are presented in table 1. Those for the other three aluminum nuclei are obtained by changing the signs of the values in any one row, which corresponds to reflection through a plane perpendicular to thea, b, or c crystal axis. It should be clear from the 466
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~\•
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~-:-‘~
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•~~/ axis •
50
1 00
150
Rotation Angle (deg
________________________________________ )c)
~b 0
/
. •-•.L •
i
\
/ a
/• .~.
1o0~ •~
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~. S
/ /
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• ~•—•
•~S
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200
/
/
•
/•\ •
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/ ‘~.-/~otation axis c-
__________________________________________ 0
50 100 Rotation Angle ldeg.l
150
Fig. 2. A typical set of rotation curves showing the variation in the splitting between the center line and the first satellite as the crystal was particular rotated about of the three orthogonal crystal axes. This data each set was measured at —15°C. The solid curves indicate the theoretical fit to the data from which the coupling constant, asymmetry parameter and principal axis cosines were determined.
Volume 91A, number 9
PHYSICS LETTERS
11 October 1982
Table 1 27A1 quadrupole coupling parameters as a function of temperature. T (°C)
e2qQ/h (MHz)
Direction cosine matrix Y
2
0.505 —0.802 0.320
—0.396 0.115 0.911
0.767 0.587 0.260
30
1.430
0.748
—15
1.483
0.689
0.542 —0.806 0.238
—0.323 0.062 0.944
0.776 0.589 0.227
—60
1.501
0.675
0.542 —0.801 0.230
—0.315 0.054 0.947
0.771 0.596 0.223
—105
1.532
0.673
0.560 —0.800 0.215
—0.308 0.040 0.951
0.769 0.599 0.224
—150
1.554
0.665
0.565 —0.802 0.192
—0.306 0.012 0.952
0.766 0.597 0.239
direction cosines that the Y principal axis of the quadrupole tensor lies nearly along the c crystal axis, while the land Z principal axes (the smallest and largest) lie dependence roughly in the plane.onAstemperature can be seenisin fig. 3, the of ab e2qQ/h linear over the region studied within the accuracy of the experiment. On the other hand, i~rapidly falls from its value of 0.748 at 30°Ctoward an2qQ/h asymptotic on T value of 0.663. A linear dependence of e I
I I
0.8
YAIO3 1.6
IMHzI
0.6 1.5
a b c
x
is also seen over the same temperature range for both 1391_a and 27AJ in LaAlO 3 [7], which has the undistorted perovskite structure. 27A1 Very little NMR data has with been YAIO published on in compounds iso-structural 3. Grochulski et al. [8] reported an aluminum tensor in YA1O3 at room temperature, but we have been unable to find any agreement between results and ours. Onand the other hand, Boesch et al.their [61 reported TI = 0.876 the direction cosines given in table 2 for aluminum in GdAIO 3, which compare well with our results, exceptthe that the hand, X and the Y principal areMHz, interchanged. On other value they report for 2qQ/hwhich =axes 0.544 differs the coupling constant, e from our result bylarge roughly a factor of three, which is an unexpectedly difference.
t~_° ~
Table 2 ~
-i~o -~o -~o
~
~o
Direction cosines for aluminum in GdAIO 3.
Tl~C)
2qQ/h and the asymmetry Fig. 3. The quadrupole parameter iicoupling as functions constant of temperature. e A straight line has been fit through the e2qQ/h data, while a smooth curve has been drawn through the asymmetry parameter data.
x
___________________
a b c
—0.438 0.134 0.889
______
Y 0.595 —0.698 0.398
_______________
2 0.674 0.703 0.226
467
Volume 91A, number 9
PHYSICS LETTERS
References [1] R.M. Shelby, R.M. Macfarlane and R.L. Shoemaker, 3~,Phys. Two-pulse photon echo June ENDOR of YA1O Rev. B, to be published 1, 1982. 3 :Pr [21 D.P. Buium, R.M. Macfarlane and R.M. Shelby, Phys. Lett. 90A (1982) 483. [31 S.GellerandE.A.Wood,ActaCryst.9(1956)563; R. Diehi and G. Brandt, Mat. Res. Bull. 10 (1975) 85. [4] A.J. Highe, Ionic motion in solid electrolytes: a solid state NMR study of sodium and lithium in Il-alumina, Ph.D. Dissertation, Calif. Inst. of Tech. (1981); Diss. Abs. mt. 41(1981) 4134B.
468
11 October 1982
[5] eds. M.H.F.Cohen Seitz and F. D. Reif, Turnbull in: Solid (Academic state physics, Press, New Vol.5, York, 1957) p. 321. [6] H.R. Boesch, E. Brun and B. Derighetti, Helv. Phys. Acta 41(1968) 417. [7] K.A. Mueller, E. Brun, B. Derighetti, J.E. Drumheller and F. Waldner, Phys. Lett. 9 (1964) 223; F. Borsa, M.L. Crippa and B. Derighetti, Phys. Lett. 34A(1971)5. [8] T. Grochuiski and W. Zbieranowski, in: Magn. Reson. Relat. Phenom., Proc. 20th Congr. AMPERE, Tallinne, USSR, eds. E. Kundla, E. Lippmaa and T. Saluvere (Springer, Berlin, 1979) p. 192.
PHYSICS LETTERS
11 October 1982
TEMPERATURE DEPENDENCE OF 27M NMR IN YA1O3 D.P. BURUM, R.M. MACFARLANE, R.M. SHELBY IBM Research Laboratory, 5600 Cottle Rd., San Jose, CA 95193, USA
and L. MUELLER NMR Regional Facility, California Institute of Technology, Pasadena, C’! 91125, USA Received 26 April 1982 Revised manuscript received 15 July 1982 27A1 in yttrium ortho-aluminate has been measured between 30°Cand —150°C.The coupling The nuclear constant quadrupole e2qQ/h varies tensor linearly for from 1.44 to 1.56 MHz over this range, whereas the asymmetry parameter i~drops rapidly from 0.748 toward an asymptotic value of 0.663.
In our application of photon echo nuclear double resonance (PENDOR) to rare-earth ions doped into crystals of YA1O 3 at 2 K we found that we could detect not only the magnetic resonance of the rare-earth nuclei [1], but also the NQR spectra of those aluminum nuclei immediately surrounding the spectra impurity 27Al PENDOR were ions [2]. Since different obtained for different species of rare earth,it was clear that the crystal field was distorted at the nearest
nuclei per unit cell. However, the symmetry of the crystal is such that only two quadrupole multiplets are observed whenever the magnetic field is perpendicular to one of the three orthogonal crystal axes, and these two patterns collapse into a single multiplet when the field the is parallel a crystal axis. Therefore, for simplicity, crystalto axes were chosen as the rotation axes for the experiment. A single crystal of YA1O 3 was used for all the measurements, which were performed at 52.12 MHz. The crystal, which contained some color centers that helped to shorten T1 (the crystal was light brown in color), was shaped into a ~3 mm cube rounded edges and held firmly in a teflon sectionplugs. of 5 mm glass tubing by two The (ID) glass thin tubewalled in turn fit into the goniometer of a variable temperature NMR probe which has been described elsewhere [4]. Spectra such as that shown in fig. 1 were taken 18
neighbor aluminum sites by the substitution of a rare earth ion for an yttrium. In this letter we report on the of an NMR study which we performed on 27Mresults in YAIO 3 over the temperature range 30 to —150°Cin order to determine the27A1 unperturbed 27~ NQR frequenNQR frequencies. The zero field cies at 2 K derived from these NMR results are compared with our PENDOR data elsewhere [2]. Because of the small 27M quadrupole splittings, it was not possible to perform zero field NQR on YA1O 3, and so it was necessary to carry out a full rotation study at high field for each temperature. Yttrium ortho-aluminate has the so-called distorted perovskite structure [3] ~‘ ,with four inequivalent aluminum *
The Geller and Wood [3] definition of the crystal axes is used throughout this letter,
degrees as the crystal was rotated successively about each of its three axes at each of five temperatures, 30, —15, —60, —105 and —150°C.For each spectrum the separation between the central line (m = 1/2 ‘~m = —1/2) and the first satellite (m = 1/2 ~÷m= 3/2) was recorded for each of the two quadrupole multiplets. The result was a set of three curves such as those shown in fig. 2 for each temperature, from which the 465
Volume 91A, number 9
PHYSICS LETTERS
____
r
I
_________
-
(2)
~Ai
(a)
11 October 1982
50
1
/ • •~ ~ •
-
/./
—
YAIO
100
3 T
.
-
150C > -
50
~
U
C
\
.
I
Rotjto. \• xis
\
\•
////
\••
S
•\
•~•~•
b
//
S
• ~
~
(I
~
50 e~
•\
-
.
—
e—
•—s •—•
-60
40
-20
0
20
40
I
60
I
0
Freqeescy Offset (kHz)
Fig. 1. A representative YA1O3 aluminum NMR spectrum. This spectrum was taken at —150°C with the field perpendicular to thea crystal axis. The two five-line quadrupole multiplets corresponding to the two inequivalent aluminum nuclei are indicated. The outermost lines in the spectrum are “folded” since their actual splitting slightly exceeded the sampling bandwidth of the spectrometer (±72kHz).
i
(li)
I
I
50 100 Rotation Angle Ideg.)
200 ~ ~
~ .‘ s-
:— ‘1~
~/
5/
:/‘~
/
* 1
150
I
LI
. J
00 \
I
\S
C
••/
/ :
S
5/
2qQ/h, the asymmetry parameter coupling i~and the constant directione cosines giving the orientations of the principal axes of the quadrupole tensor could be determined in the usual manner [5]. These results are presented in table 1, and both e2qQ/h and i~are plotted as functions of temperature in fig. 3. The analysis of the rotation curves was complicated by the high symmetry of the crystal, in that it was not possible to determine unambiguously the signs of the off-diagonal elements of the quadrupole tensor expressed in the crystal axis frame. The eight possibilities fell into two groups of four, each of which represented a set of four tensors for the four aluminum atoms in the unit cell. Within each group of four, the tensors differed only in their orientations. The values presented in table 1 and fig. 3 were chosen both on the basis of comparison with published data on an isostructural compound (GdA1O 3) [6], and because the value of i~resulting from the other possibility took on improbable values (rao.975) and behaved in an unphysical way as a function of temperature. The orientation cosines for one of the four aluminum nuclei in the unit cell are presented in table 1. Those for the other three aluminum nuclei are obtained by changing the signs of the values in any one row, which corresponds to reflection through a plane perpendicular to thea, b, or c crystal axis. It should be clear from the 466
\~ a
\~
0•
•~
1 00
•
\*~
•\
~/
~\•
b
-
-s-ET1 w397 359 m441 359 lSBT S
~-:-‘~
0
Rotat oil
•~~/ axis •
50
1 00
150
Rotation Angle (deg
________________________________________ )c)
~b 0
/
. •-•.L •
i
\
/ a
/• .~.
1o0~ •~
I
~. S
/ /
\/
S
• -
• ~•—•
•~S
I \~
200
/
/
•
/•\ •
/
\
S
/ ‘~.-/~otation axis c-
__________________________________________ 0
50 100 Rotation Angle ldeg.l
150
Fig. 2. A typical set of rotation curves showing the variation in the splitting between the center line and the first satellite as the crystal was particular rotated about of the three orthogonal crystal axes. This data each set was measured at —15°C. The solid curves indicate the theoretical fit to the data from which the coupling constant, asymmetry parameter and principal axis cosines were determined.
Volume 91A, number 9
PHYSICS LETTERS
11 October 1982
Table 1 27A1 quadrupole coupling parameters as a function of temperature. T (°C)
e2qQ/h (MHz)
Direction cosine matrix Y
2
0.505 —0.802 0.320
—0.396 0.115 0.911
0.767 0.587 0.260
30
1.430
0.748
—15
1.483
0.689
0.542 —0.806 0.238
—0.323 0.062 0.944
0.776 0.589 0.227
—60
1.501
0.675
0.542 —0.801 0.230
—0.315 0.054 0.947
0.771 0.596 0.223
—105
1.532
0.673
0.560 —0.800 0.215
—0.308 0.040 0.951
0.769 0.599 0.224
—150
1.554
0.665
0.565 —0.802 0.192
—0.306 0.012 0.952
0.766 0.597 0.239
direction cosines that the Y principal axis of the quadrupole tensor lies nearly along the c crystal axis, while the land Z principal axes (the smallest and largest) lie dependence roughly in the plane.onAstemperature can be seenisin fig. 3, the of ab e2qQ/h linear over the region studied within the accuracy of the experiment. On the other hand, i~rapidly falls from its value of 0.748 at 30°Ctoward an2qQ/h asymptotic on T value of 0.663. A linear dependence of e I
I I
0.8
YAIO3 1.6
IMHzI
0.6 1.5
a b c
x
is also seen over the same temperature range for both 1391_a and 27AJ in LaAlO 3 [7], which has the undistorted perovskite structure. 27A1 Very little NMR data has with been YAIO published on in compounds iso-structural 3. Grochulski et al. [8] reported an aluminum tensor in YA1O3 at room temperature, but we have been unable to find any agreement between results and ours. Onand the other hand, Boesch et al.their [61 reported TI = 0.876 the direction cosines given in table 2 for aluminum in GdAIO 3, which compare well with our results, exceptthe that the hand, X and the Y principal areMHz, interchanged. On other value they report for 2qQ/hwhich =axes 0.544 differs the coupling constant, e from our result bylarge roughly a factor of three, which is an unexpectedly difference.
t~_° ~
Table 2 ~
-i~o -~o -~o
~
~o
Direction cosines for aluminum in GdAIO 3.
Tl~C)
2qQ/h and the asymmetry Fig. 3. The quadrupole parameter iicoupling as functions constant of temperature. e A straight line has been fit through the e2qQ/h data, while a smooth curve has been drawn through the asymmetry parameter data.
x
___________________
a b c
—0.438 0.134 0.889
______
Y 0.595 —0.698 0.398
_______________
2 0.674 0.703 0.226
467
Volume 91A, number 9
PHYSICS LETTERS
References [1] R.M. Shelby, R.M. Macfarlane and R.L. Shoemaker, 3~,Phys. Two-pulse photon echo June ENDOR of YA1O Rev. B, to be published 1, 1982. 3 :Pr [21 D.P. Buium, R.M. Macfarlane and R.M. Shelby, Phys. Lett. 90A (1982) 483. [31 S.GellerandE.A.Wood,ActaCryst.9(1956)563; R. Diehi and G. Brandt, Mat. Res. Bull. 10 (1975) 85. [4] A.J. Highe, Ionic motion in solid electrolytes: a solid state NMR study of sodium and lithium in Il-alumina, Ph.D. Dissertation, Calif. Inst. of Tech. (1981); Diss. Abs. mt. 41(1981) 4134B.
468
11 October 1982
[5] eds. M.H.F.Cohen Seitz and F. D. Reif, Turnbull in: Solid (Academic state physics, Press, New Vol.5, York, 1957) p. 321. [6] H.R. Boesch, E. Brun and B. Derighetti, Helv. Phys. Acta 41(1968) 417. [7] K.A. Mueller, E. Brun, B. Derighetti, J.E. Drumheller and F. Waldner, Phys. Lett. 9 (1964) 223; F. Borsa, M.L. Crippa and B. Derighetti, Phys. Lett. 34A(1971)5. [8] T. Grochuiski and W. Zbieranowski, in: Magn. Reson. Relat. Phenom., Proc. 20th Congr. AMPERE, Tallinne, USSR, eds. E. Kundla, E. Lippmaa and T. Saluvere (Springer, Berlin, 1979) p. 192.