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Exchange fields

Pisani [169] has used the density of states from periodic FIP (see B3.2.2.4) slab calculations to describe the host in which the cluster is embedded, where the applications have been primarily to ionic crystals such as LiE. The original calculation to derive the external Coulomb and exchange fields is usually done on a finite cluster and at a low level of ab initio theory (typically minimum basis set FIP, one electron only per atom treated explicitly). [Pg.2225]

Fig. 3.7 The Heitler-London configuration A(1) B(2) and A(2) B(1) (a) and (b) respectively, where 0A and represent the atomic 1s orbitals centred on atoms A and respectively, and 1 and 2 represent the coordinates of the two (indistinguishable) electrons, (c) The molecular orbital basis function in the singlet state where electrons 1 and 2 have opposite spin, (d) The up and down spin eigenfunctions corresponding to local exchange fields of opposite sign on A and B. Fig. 3.7 The Heitler-London configuration A(1) B(2) and A(2) B(1) (a) and (b) respectively, where 0A and represent the atomic 1s orbitals centred on atoms A and respectively, and 1 and 2 represent the coordinates of the two (indistinguishable) electrons, (c) The molecular orbital basis function in the singlet state where electrons 1 and 2 have opposite spin, (d) The up and down spin eigenfunctions corresponding to local exchange fields of opposite sign on A and B.
It is important that in the absence of an exchange field J (or magnetization M) acting on spins, the SC, i.e. the function fa, exists both in the superconducting and normal (non-magnetic) layers. If J is not equal to zero but is uniform in space and directed along the z-axis, then the part fa of the TC arises in the structure. [Pg.232]

The observed magnetization value may be used to calculate the average distance between the reversed spins. Therefore the M(H) curve, measured in experiment, in principle allows one to obtain the dependence of the effective exchange field on the spacing between interacting spins Heff(r). The measured magnetization curve (Fig. 13), however,... [Pg.90]

Figure 16. Distribution of effective exchange fields, produced by ions with reversed spins in the (111) plane [9,10]. Figure 16. Distribution of effective exchange fields, produced by ions with reversed spins in the (111) plane [9,10].
CHANGE OF CURIE TEMPERATURE AND EFFECTIVE EXCHANGE FIELDS IN FERRIMAGNETIC R2Fe14B COMPOUNDS UPON HYDROGENATION... [Pg.599]

Keywords rare-earth compounds, hydride, magnetic ordering temperature, exchange field... [Pg.599]

Here Ni and N2 are the numbers of Fe and R atoms per mole, respectively gi and g2 are the corresponding Lande factors G - is de Gennes factor hn, h22 and h21 -effective exchange fields, Si is spin of Fe ions, Z22 is the number of R neighbors of each R atom, A22 - is the exchange interaction integral of R atom with R neighbors. [Pg.602]

The obvious merit of Eq. (9) is the explicit dependence of the Curie temperature on the de Gennes factor and the possibility to estimate the exchange field h2 from the Fe sublattice acting on the rare-earth ions. [Pg.602]

Hydrogenation does not practically change the exchange field h22 within the R - sublattice. [Pg.603]

Nikitin S.A., Tereshina I.S. (2003) Effect of interstitial atoms on the effective exchange fields in ferromagnetic rare-earth and 3d transition metal compounds R2Fen andRFenTi. Fizikatverdogo tela 45(10), 1850-1856. [Pg.604]

Nikitin S.A., Bisliev A.M. (1975) Effective exchange fields in rare-earth - iron compounds RFe2 and RFe3. Vestnik MGU 2, 195-200. [Pg.604]

In 2-D and 1-D systems even in non-uniaxial materials, the Neel model can still be used since the anisotropic field in the plane where the moments can rotate is small compared with the exchange field in the perpendicular direction. After first considering the particular case of CsNiF3, we will described several 2-D and 1-D Heisenberg fluorides showing spin-flop behavior. [Pg.136]


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