1989 Fiscal Year Final Research Report Summary
Deviation from the S-state of Eu^<2+> ion in magnetic materials due to relativistic effect of f electrons
| Project/Area Number |
63540256
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Department of Physics, Kagoshima University |
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Principal Investigator |
KAWAKAMI M. Kagoshima Univ., Department of Physics, Associate Professor, 理学部, 助教授 (60004389)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAKAMI M. Kagoshima Univ., Department of Physics, Associate Professor (60004389)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Nuclear Magnetic Resonance / Hyperfine Field / EuTe / EuSe / Nuclear Quadrupole Interaction / Relativistic Effect / Magnetoelastic Effect / Magnetostriction |
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| Research Abstract |
It is known that the excited states generally mix into the ground state of f electrons by the relativistic effect. Since Eu^<2+> ion has the ground S state which is spherically symmetric, the effect can be easily seen. In this study we tried to find this effect through the observation of the quadrupole splitting in the NMR spectrum of the Eu nuclei. The splitting is proportional to the electric field gradient at the nuclei, which consists of the lattice contribution and the contribution arising from the asymmetry of the electronic charge of the Eu atom itself. We studied EuX (X=O, Te) of the cubic NaCl type, in which the lattice contribution is very small. Using a single crystal of EuTe, we observed ^<151>Eu and ^<153>Eu NMR spectrum in liquid helium temperatures in magnetic fields up to 21 kOe by means of the steady state method. Above 6 kOe, ^<151>Eu NMR exhibited a single line, but ^<153>Eu NMR exhibited a five-line splitting which attributable to the quadrupole interaction. The variation of the spectrum with the crystal direction was measured. The spectrum for [100] was symmetric. The magnitude of the splitting decreased rather rapidly with increasing temperature. The relativistic effect could not be separated, but with the use of the value from the previous ENDOR measurements of Eu^<2+> in CaF_2 we analyzed the magnitude of the quadrupole splitting as a sum of the relativistic effect and the contribution from the magnetoelastic effect. The analysis gave important information of the magnetostriction in antiferromagnetic EuTe. For EuO the splitting was not observed, which indicates that the sample used was not so pure. The temperature dependence of the splitting in EuSe was also presented.
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