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Pauli Paramagnetism in Metals with High Densities of States*L

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Pauli Paramagnetism in Metals with High Densities of States*L JOURNAL OF RESEARCH of the National Bureau of Standards-A. Physics and Chemistry Vol. 74A, No. 4, July-August 1970 Pauli Paramagnetism in Metals with High Densities of States*l S. Foner Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (October 10, 1969) Because the Pauli paramagnetic susceptibility of alloys have permitted considerable progress to be a free electron gas, x~ is proportional to the density of made. The properties of these systems are reviewed states N(O) at the Fermi energy, it is expected that mea­ and estimates of N(O) and V are examin ed. Here qualita­ surements of X~ of metals and alloys can yield a tive and quantitative comparisons of various experi­ reasonable measure of N(O). If xg can be measured ments can be made. The possibilities of applying large directly, then N(O) can be determined with high accura­ magnetic fields and thereby independently measuring cy. The major obstacle to this procedure is that the N(O) and small changes of N(O) near the Fermi energy measured static susceptibility Xi, = xV(l-N(O)V)=xgD by such studies are discussed. Recent theories which (for the Stoner model) where V is a measure of the elec­ examine the changes of Xv with alloying are also com­ tron-electron interaction potential. Unfortunately, V is pared with experimental results. not easily determined experimentally, or theoretically, A few useful references for relevant recent papers so that measurements of Xv do not yield accurate mea­ concerning the susceptibility of nearly ferromagnetic sures of N(O). More detailed (realistic) models involve metals and alloys are tabulated in references 1 to 4. additional parameters which are also not accurately Recent detailed band calculations in Pd have been re­ determined. Thus direct measurements of Xv can yield ported in references 5 to 8. Several papers at this con­ a measure of N(O), but these values of N(O) are subject ference also deal with high densities of states materials. to the uncertainties of various parameters in the theo­ ries. In this talk we discuss the present status of experi­ ments and theories of Xv in metals and alloys with low 1. References N(O) where D is generally near unity, and high N(O) where D is expected to be large. Comparisons with in­ [1] Foner, 5., Freeman, A. J. , Blum, N., Frankel, R. B. , McNiff, E. J. , dependent low-temperature electronic specific heat Jr., and Praddaude, H., Phys. Rev. 181,863 (1969). measurements are discussed and attempts to derive [2] Foner, 5., and McNiff, E. J. , Jr., Phys. Rev. Letters 19, 1438 N(O) from both susceptibility and specific heat are (1967). reviewed. [3] Foner, 5., and McNiff, E. J., Jr., Phys. Letters 29A, 28 (1969). [4] Doclo, R. , Foner, 5., and Narath, A. , J. App!. Phys. 40,1206 Many recent investigations of metals and alloys with (1969). high densities of states have been of great interest [5] Mueller, F. M., Freeman, A. ]., Dimmock, 1. 0., and Furdyna, because such systems start to approach ferromagnetic A. (to be published). order. The properties of Pd have been investigated ex­ [6] Hodges, L., Ehrenreich, H. , and Lang, N. D. , Phys. Rev. 152, tensively and very detailed band calculations now exist. 505 (1966). [7] Anderson, O. K., and Mackintosh, A. R. , Soli d State Co mm. The large exchange enhancements in this metal and its 6,285 (1968). [8] Misetich, A. A. , and Watson, R. E., 1. App!. Phys. 40, 1211 (1969). *An invited paper presented at the 3d Materials Research Sym­ pos ium , Electronic Density of States, November 3-6, 1969, Gaithersburg, Md. I Supported by the U.S. Air Force Office of Scientific Research. (Paper 74A4-623) 567 .
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