Local spin order

In order to measure of equation (11b) frequency or field dependent for frequencies greater than 5 MHz, where the standard technique no longer works, Bq must be varied over the relaxation period the generation and detection of the local spin order can be achieved under any suitable high-field condition. We realized this possibility with two of our FC spectrometers by a Bq cycle with a fast field switch Bpi from the polarization to the relaxation field at the beginning of the relaxation period (t2 interval), and the inverse switch Bp from the relaxation to the detection field Bp = Bp at the end of the T2 interval. The extended Jeener sequence... 

In order to perform the calculation., of the conductivity shown here we first performed a calculation of the electronic structure of the material using first-principles techniques. The problem of many electrons interacting with each other was treated in a mean field approximation using the Local Spin Density Approximation (LSDA) which has been shown to be quite accurate for determining electronic densities and interatomic distances and forces. It is also known to reliably describe the magnetic structure of transition metal systems. 

Table4.4 Spectroscopic properties for Au2 q= -1,0, + 1) using ab-initio (Hartree Fock, HF, second-order Moller-Plesset, MP2, and coupled cluster, CCSD(T)) and DFT (local spin-density approximation, LSDA, Perdew-Wang CCA, PW91, and Becke three-parameter Lee-Yang-Parr functional, B3LYP) methods at the RPPA level of theory.

In order to present the derivation of local spin expectation values, we shall briefly recall the foundations of spin eigenvalue equations in the non-relativistic framework. Information on the spin states of a molecule can be extracted from either the total spin operator S2 or its -component Sz (i.e., from its projection on the -axis),... 

In order to obtain expressions for the local spin expectation values, different decomposition schemes exist. One may either partition the total spin expectation value (S2) (122,124) as suggested by Mayer or the total spin operator S2 (113,114) as proposed by Clark and Davidson. The corresponding decomposition schemes for multi-determinant wave functions may be found in Refs. (125-127). 

Before investigating of long-range correlations of Jahn-Teller distortion using equation (37), we analyse in addition the effect of the exchange interaction between localized spins on the ordering of these distortions. 

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