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Electron spin resonance of Mn2+ ions in perovskite-type crystal of KMgCl3
Volume 24A, number 10
tl
in\
PHYSICS
-------
LETTERS
and for others - CT ‘* on (a,, and u cross section for capture o P the electron an x hole, respectively). With the increasing of injection levels proceeds the preferential filling of each level and on the current-voltage characteristics a suitable negative resistance appears. an ‘.“UP,
------
-_____
Id’..
2
----_-__
uu
d I9
: I?
:
: 19
:
: 21
8 May 1967
: 23
:
: 29
:
: 22
: 29
4
The authors wish to thank 0. V. Konstantinov for taking part in discussing the results.
Fig. 2. The oscillations of current-voltage dependence of alloyed GaP p-n junction (forward bias). T = 300°K. The presence of deep recombination centers and traps was discussed in ref. 3. The appearance of oscillations on the current-voltage characteristics (fig. 2) can indicate the effectivity of several impurity levels serving as trapping centers. One can represent, the picture quality of “terrace” consecutive filling of suitable impurity centers El. E2. Eg. E4 etc. In this case one of these levels may lie in the upper half of the forbidden gap. others - in the lower half, so that for some -
References
1. M.A. Lampert. Progress in semiconductors, 1965. 2. V. I.Stafeev. Fiz.Tv. Tela 3 (1961) 2513. 3. R. F. Mamedova. S. V. Slobodchikov “Uchenie zapiski” Aserb. Gos. University, no. 4 (1965) pp. 61-66.
*****
ELECTRON SPIN RESONANCE OF IN PEROVSKITE-TYPE CRYSTAL
Institute Czechoslovak
Mn2+ IONS OF KMgC13
K. ZbdLNSK? of Radio Engineering and Electronics. Academy of Sciences. Prague. Czechoslovakia Received 24 March 1967
The ESR spectrum of Mn2- in KMgC13 at room temperature was fitted by the spin-Hamiltonian of tetragonal symmetry. The values of the parameters of this spin-Hamiltonian were determined. The signs of D- and a- parameters were estimated relatively to the hyperfine structure parameters which were presumed to be negative. Some time ago the results of electron spin resonance study of the double salt KMnC13 were published [l]. On the basis of the analogy between the temperature dependence of ESR of KMnC13 and that of the known perovskite KMnF3 crystal it was estimated that KMnC13 is probably of a perovskite-type structure. Quite recently the structure of KMgC13 was determined from a Debye-Scherrer pattern [2] with the conclusion that the aton& arrangement in KMgC13 is an orthorhombic distortion of the perovskite-type 498
structure. Thus both salts, KMgC13 and KMnC13 are evidently of the perovskite-type structure which is also supported by the small difference between the ionic radia of Mn2+ and Mg2+ ions. This fact predetermines the KMgC13 as a suitable diluent of KMnC13 for performing ESR measurements of Mn2+ ions. In this letter the spin-Hamiltonian of the ground state of Mn2+ ion in KMgC13 is reported as a basis for further electron-nuclear double resonance studies. The KMgC13 compound was prepared from the
Volume 24A. number
PHYSICS
10
mixture of NIQCl. MgCI. 6H2O and KC1 salts. The single crystals were grown from the melt by the method of Bridgman in evacuated fused silica ampules. About 0.5 mol % of MnCl2 was added into the melt. The crystals were oriented according to the resolved cleavable planes. Evidently two types of the cleavable planes are observed; they are the (100) and (110) planes. An X-band ESR spectrometer with the magnetic field modulation at 960 kHz and with the cylindrical transmission cavity was used in the measurements. The magnetic field was determined by the temperature controlled Hall probe of InSb calibrated by the nuclear magnetic resonance of protons in water. All measurements were performed at room temperature. More unequivalent spectra were observed in the sample which was cleaved from the crystal boule, but one of the spectra is one or two orders of magnitude more intensive than the others. The intensity ratio of the main spectrum to the additional spectra differs at different samples. The origin of additional spectra is not quite clear. We assume that the-single crystals are difficult to obtain due to the phase transition between llO” and 1750C [2]. Thus the experiments were performed on randomly oriented specimens. the major part of each sample being single crystalline in nature. The spectrum of Mn2’ in KMgC13 may be expressed by the spin-Hamiltonian of the tetragonal symmetry along the [loo] axis: = g,,~HzS,+gL~(HxSx + AS,&
8 Nay 1967
LETTERS
measurements of the ESR spectra with the magnetic field parallel to [OOlJ., [l@q] .and (llO] directions and they are equal :to g
= 1.9996 f O.BOl9
g,. =2.0010* D =+90.8
0.0010 +0.2rlO-4cm
A=-81.5*
0.2x10-4cm-1
B=-82.4*
0.2 x10-4cm-1
ff=-0.7i
-1
0.1 x10-4cm-1
The signs of D and II parameters were determined relatively to the A and Bparameters which are presumed to be negative. The value of n was estimated from the differences between the positions of the resonance lines when the magnetic field is oriented along the [loo] and [llO] directions. When rotating the magnetic field in the (001) crystal plane, the tetragonal axis of the spectrum is quite evident. The tetragonal symmetry of the crystal is in a disagreement with the measurement of the Debye-Sherrer pattern of KMgC13 [2]. On the other hand, it is interesting that the KMnC13 crystal is just of the tetragonal symmetry [3]. The author is indebted to Dr. F. Kubec for his kind assistance in measurements of the magnetic field and to Miss M. Vespalcova for preparing the crystals.
+ HySy) + D[S,2 - +S(S +I)] +
+B(S,,Jx+SyIy)
+a(S.j+S;,+S;,
,
(1)
where the eigenvalue of the electron spin is S =$. that of the nuclear spin is I =f and 6 is the Bohr magneton. The values of the parameters in the spin-Hamiltonian (1) were determined from the
References 1. K. Zda’nsky. E. Simgnek and Z. Qroubek. Phys. Stat. Solidi 3 (1963) K 277. H. L.Yakel and G. 1’. Smith. J. Chem. 2. J. Brynestad. Phys. 45 (1966) 4652. 3. R. W. Kedzie. J. R. Shane. M. Kestigian and W. J. Croft. J.AppI. Phys. 36 (1965) 1195.
*****
499
tl
in\
PHYSICS
-------
LETTERS
and for others - CT ‘* on (a,, and u cross section for capture o P the electron an x hole, respectively). With the increasing of injection levels proceeds the preferential filling of each level and on the current-voltage characteristics a suitable negative resistance appears. an ‘.“UP,
------
-_____
Id’..
2
----_-__
uu
d I9
: I?
:
: 19
:
: 21
8 May 1967
: 23
:
: 29
:
: 22
: 29
4
The authors wish to thank 0. V. Konstantinov for taking part in discussing the results.
Fig. 2. The oscillations of current-voltage dependence of alloyed GaP p-n junction (forward bias). T = 300°K. The presence of deep recombination centers and traps was discussed in ref. 3. The appearance of oscillations on the current-voltage characteristics (fig. 2) can indicate the effectivity of several impurity levels serving as trapping centers. One can represent, the picture quality of “terrace” consecutive filling of suitable impurity centers El. E2. Eg. E4 etc. In this case one of these levels may lie in the upper half of the forbidden gap. others - in the lower half, so that for some -
References
1. M.A. Lampert. Progress in semiconductors, 1965. 2. V. I.Stafeev. Fiz.Tv. Tela 3 (1961) 2513. 3. R. F. Mamedova. S. V. Slobodchikov “Uchenie zapiski” Aserb. Gos. University, no. 4 (1965) pp. 61-66.
*****
ELECTRON SPIN RESONANCE OF IN PEROVSKITE-TYPE CRYSTAL
Institute Czechoslovak
Mn2+ IONS OF KMgC13
K. ZbdLNSK? of Radio Engineering and Electronics. Academy of Sciences. Prague. Czechoslovakia Received 24 March 1967
The ESR spectrum of Mn2- in KMgC13 at room temperature was fitted by the spin-Hamiltonian of tetragonal symmetry. The values of the parameters of this spin-Hamiltonian were determined. The signs of D- and a- parameters were estimated relatively to the hyperfine structure parameters which were presumed to be negative. Some time ago the results of electron spin resonance study of the double salt KMnC13 were published [l]. On the basis of the analogy between the temperature dependence of ESR of KMnC13 and that of the known perovskite KMnF3 crystal it was estimated that KMnC13 is probably of a perovskite-type structure. Quite recently the structure of KMgC13 was determined from a Debye-Scherrer pattern [2] with the conclusion that the aton& arrangement in KMgC13 is an orthorhombic distortion of the perovskite-type 498
structure. Thus both salts, KMgC13 and KMnC13 are evidently of the perovskite-type structure which is also supported by the small difference between the ionic radia of Mn2+ and Mg2+ ions. This fact predetermines the KMgC13 as a suitable diluent of KMnC13 for performing ESR measurements of Mn2+ ions. In this letter the spin-Hamiltonian of the ground state of Mn2+ ion in KMgC13 is reported as a basis for further electron-nuclear double resonance studies. The KMgC13 compound was prepared from the
Volume 24A. number
PHYSICS
10
mixture of NIQCl. MgCI. 6H2O and KC1 salts. The single crystals were grown from the melt by the method of Bridgman in evacuated fused silica ampules. About 0.5 mol % of MnCl2 was added into the melt. The crystals were oriented according to the resolved cleavable planes. Evidently two types of the cleavable planes are observed; they are the (100) and (110) planes. An X-band ESR spectrometer with the magnetic field modulation at 960 kHz and with the cylindrical transmission cavity was used in the measurements. The magnetic field was determined by the temperature controlled Hall probe of InSb calibrated by the nuclear magnetic resonance of protons in water. All measurements were performed at room temperature. More unequivalent spectra were observed in the sample which was cleaved from the crystal boule, but one of the spectra is one or two orders of magnitude more intensive than the others. The intensity ratio of the main spectrum to the additional spectra differs at different samples. The origin of additional spectra is not quite clear. We assume that the-single crystals are difficult to obtain due to the phase transition between llO” and 1750C [2]. Thus the experiments were performed on randomly oriented specimens. the major part of each sample being single crystalline in nature. The spectrum of Mn2’ in KMgC13 may be expressed by the spin-Hamiltonian of the tetragonal symmetry along the [loo] axis: = g,,~HzS,+gL~(HxSx + AS,&
8 Nay 1967
LETTERS
measurements of the ESR spectra with the magnetic field parallel to [OOlJ., [l@q] .and (llO] directions and they are equal :to g
= 1.9996 f O.BOl9
g,. =2.0010* D =+90.8
0.0010 +0.2rlO-4cm
A=-81.5*
0.2x10-4cm-1
B=-82.4*
0.2 x10-4cm-1
ff=-0.7i
-1
0.1 x10-4cm-1
The signs of D and II parameters were determined relatively to the A and Bparameters which are presumed to be negative. The value of n was estimated from the differences between the positions of the resonance lines when the magnetic field is oriented along the [loo] and [llO] directions. When rotating the magnetic field in the (001) crystal plane, the tetragonal axis of the spectrum is quite evident. The tetragonal symmetry of the crystal is in a disagreement with the measurement of the Debye-Sherrer pattern of KMgC13 [2]. On the other hand, it is interesting that the KMnC13 crystal is just of the tetragonal symmetry [3]. The author is indebted to Dr. F. Kubec for his kind assistance in measurements of the magnetic field and to Miss M. Vespalcova for preparing the crystals.
+ HySy) + D[S,2 - +S(S +I)] +
+B(S,,Jx+SyIy)
+a(S.j+S;,+S;,
,
(1)
where the eigenvalue of the electron spin is S =$. that of the nuclear spin is I =f and 6 is the Bohr magneton. The values of the parameters in the spin-Hamiltonian (1) were determined from the
References 1. K. Zda’nsky. E. Simgnek and Z. Qroubek. Phys. Stat. Solidi 3 (1963) K 277. H. L.Yakel and G. 1’. Smith. J. Chem. 2. J. Brynestad. Phys. 45 (1966) 4652. 3. R. W. Kedzie. J. R. Shane. M. Kestigian and W. J. Croft. J.AppI. Phys. 36 (1965) 1195.
*****
499