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94. Electron spin-lattice relaxation times
PARAMAGNETISM
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manganous salt, which has normal tendency of dpsL/dHc. The magnetic specific heat b/C is determined in the above mentioned salts and in NiSiFs.6H~O using single crystal samples. Quite unexpected results have been found in NiSiFs. 6H20 showing an anisotropy in b/C. These facts are considered by T. M o r i y a to show the difficulty to use Casimir-du Pr6's theory where it is assumed that the spin temperature T, is always established.
93. I m p u r i t y s p i n r e l a x a t i o n via the c o n d u c t i o n A. HONIG. Syracuse University, Syracuse (N.Y.), U.S.A.
e l e c t r o n s in s i l i c o n *).
The impurity electron spin relaxation time in phosphorous doped silicon has been measured as a function of incident infrared radiation power having a room temperature black body spectral distribution. This relaxation is presumably brought about by the conduction electrons which are produced by photoionization of the impurity atoms. Of several existing interaction mechanisms 1) 2), the spin exchange mechanism given by P i n e s , B a r d e e n and S l i c h t e r 1) yields the largest relaxation rate. For an incident infrared power of 4 × 10-9 watt, the bound electron spin relaxation time was reduced from 15 minutes (zero infrared radiation power) to 4 minutes. Assuming a photon absorption probability of unity, one obtains the ~-~10e/cm8 conduction electron concentration required by the spin exchange mechanism for a 4 minute relaxation time if the conduction electron lifetime against trapping is about 0.5 microsecond. This trapping lifetime appears reasonable, though no direct measurements have yet been made. I t has also been found t h a t the relaxation rate is proportional to the incident infrared power, and hence to the concentration of conduction electrons. 1) Pines, Bardeen, and Slichter, Phys. Rev. 106 (1957) 489. 2) Abrahams, E., Phys. Rev. 107 (1957) 491. *) Work supported by the U.S. Air force Office of Scientific Research and by a Grant from the Research Corporation. 94. E l e c t r o n s p i n - l a t t i c e r e l a x a t i o n t i m e s . M. W. P. STRANDBERG,C. F. DAVIS and R. L. KYHL. Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, U.S.A. A discussion of the experimental problems encountered in making spin-lattice relaxation measurements in electron paramagnetic systems at low temperature is presented. Gadolinium and chrome ion spin-lattice relaxation times measured by a pulse saturation technique in the time domain, are given. The relation of these spin-lattice relaxation times with relaxation times measured in the frequency domain b y observing a saturation parameter is discussed.
95. S a t u r a t i o n of p a r a m a g n e t i c r e s o n a n c e in CuK2(SO4) 2 6 H 2 0 and C r K ( S O ) 2 12H~O. B. BOLGER, K. J. VAN DAMME, J. M. NOOTHOVENVAN GOORand C. J. C-ORTER. Kamerlingh Onnes Laboratorium, Leiden, Nederland. I n view of the existing discrepancies between the relaxation times derived from the direct relaxation method and from the saturation method, a series of saturation experiments have been performed with a microwave bridge at 9400 MHz. According to
S 163
manganous salt, which has normal tendency of dpsL/dHc. The magnetic specific heat b/C is determined in the above mentioned salts and in NiSiFs.6H~O using single crystal samples. Quite unexpected results have been found in NiSiFs. 6H20 showing an anisotropy in b/C. These facts are considered by T. M o r i y a to show the difficulty to use Casimir-du Pr6's theory where it is assumed that the spin temperature T, is always established.
93. I m p u r i t y s p i n r e l a x a t i o n via the c o n d u c t i o n A. HONIG. Syracuse University, Syracuse (N.Y.), U.S.A.
e l e c t r o n s in s i l i c o n *).
The impurity electron spin relaxation time in phosphorous doped silicon has been measured as a function of incident infrared radiation power having a room temperature black body spectral distribution. This relaxation is presumably brought about by the conduction electrons which are produced by photoionization of the impurity atoms. Of several existing interaction mechanisms 1) 2), the spin exchange mechanism given by P i n e s , B a r d e e n and S l i c h t e r 1) yields the largest relaxation rate. For an incident infrared power of 4 × 10-9 watt, the bound electron spin relaxation time was reduced from 15 minutes (zero infrared radiation power) to 4 minutes. Assuming a photon absorption probability of unity, one obtains the ~-~10e/cm8 conduction electron concentration required by the spin exchange mechanism for a 4 minute relaxation time if the conduction electron lifetime against trapping is about 0.5 microsecond. This trapping lifetime appears reasonable, though no direct measurements have yet been made. I t has also been found t h a t the relaxation rate is proportional to the incident infrared power, and hence to the concentration of conduction electrons. 1) Pines, Bardeen, and Slichter, Phys. Rev. 106 (1957) 489. 2) Abrahams, E., Phys. Rev. 107 (1957) 491. *) Work supported by the U.S. Air force Office of Scientific Research and by a Grant from the Research Corporation. 94. E l e c t r o n s p i n - l a t t i c e r e l a x a t i o n t i m e s . M. W. P. STRANDBERG,C. F. DAVIS and R. L. KYHL. Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, U.S.A. A discussion of the experimental problems encountered in making spin-lattice relaxation measurements in electron paramagnetic systems at low temperature is presented. Gadolinium and chrome ion spin-lattice relaxation times measured by a pulse saturation technique in the time domain, are given. The relation of these spin-lattice relaxation times with relaxation times measured in the frequency domain b y observing a saturation parameter is discussed.
95. S a t u r a t i o n of p a r a m a g n e t i c r e s o n a n c e in CuK2(SO4) 2 6 H 2 0 and C r K ( S O ) 2 12H~O. B. BOLGER, K. J. VAN DAMME, J. M. NOOTHOVENVAN GOORand C. J. C-ORTER. Kamerlingh Onnes Laboratorium, Leiden, Nederland. I n view of the existing discrepancies between the relaxation times derived from the direct relaxation method and from the saturation method, a series of saturation experiments have been performed with a microwave bridge at 9400 MHz. According to