Magnetic ions

Because the neutron has a magnetic moment, it has a similar interaction with the clouds of impaired d or f electrons in magnetic ions and this interaction is important in studies of magnetic materials. The magnetic analogue of the atomic scattering factor is also tabulated in the International Tables [3]. Neutrons also have direct interactions with atomic nuclei, whose mass is concentrated in a volume whose radius is of the order of... 

Fxo. 12-4. The Nonmagnetic Unit Cell of MnF2 Showing the Positions of the Ion Sites. The fourfold axis is in the direction %. 0, magnetic ion 0> non-... 

Fig. 12-5. The Magnetic Unit Cell of MnFa Showing the Spin Orientation of the Magnetic Ions. The fourfold axis is in the direction of the spin vectors. The nonmagnetic ions are not shown.

On the basis of the observations, the enhancements of the p-values for the Q-Zni x MrLxS monolayer films can most likely be ascribed to the interaction between Mn ion as a magnetic ion and the external magnetic field. The enhancements are probably caused by magnetic orientation of the Q-Zni-xiMn S on the quartz substrates. 

The dipole and exchange interactions of an ion, i, with the neighboring magnetic ions, j, can be described by the Hamiltonians Hdd and Hex... 

The dipole interaction depends on the distance between the ions (6.4). Therefore, the transition probability increases with increasing concentration of magnetic ions. Studies of the concentration dependence of the relaxation can be conveniently performed on samples of amorphous frozen solutions with a uniform distribution... 

Stevens, K.W.H. 1997. Magnetic Ions in Crystals. Princeton, NJ Princeton University Press. 

Research on multi-qubit molecules starts with the synthesis and characterization of systems that seem to embody more than one qubit, for example, systems with weakly coupled electron spins. Indeed, many molecular structures include several weakly coupled magnetic ions [76-78]. On a smaller scale, the capability of implementing a Controlled-NOT quantum logic gate using molecular clusters... 

Hutchings, M.T. (1964) Point-charge calculations of energy levels of magnetic ions in crystalline electric. Fields Solid State Phys., 16, 227-273. 

All these salts contain crystallization water which assure a large distance (about 1 nm on CMN) among the magnetic ions giving a low Tc [1]. 

In summary, NMR techniques based upon chemical shifts and dipolar or scalar couplings of spin-1/2 nuclei can provide structural information about bonding environments in semiconductor alloys, and more specifically the extent to which substitutions are completely random, partially or fully-ordered, or even bimodal. Semiconductor alloys containing magnetic ions, typically transition metal ions, have also been studied by spin-1/2 NMR here the often-large frequency shifts are due to the electron hyperfine interaction, and so examples of such studies will be discussed in Sect. 3.5. For alloys containing only quadrupolar nuclei as NMR probes, such as many of the III-V compounds, the nuclear quadrupole interaction will play an important and often dominant role, and can be used to investigate alloy disorder (Sect. 3.8). 

The electron hyperfine interaction thus has important effects on both NMR relaxation and frequency shifts, and can provide valuable information on the incorporation of magnetic ions into semiconductor lattices and the resulting electronic structure as characterized by transferred hyperfine constants. Examples in Sect. 4 will show how the possible incorporation of magnetic ions into semiconductor nanoparticles can be studied by NMR. 

Nanoparticles of dilute magnetic semiconductors have also been studied by NMR. Here one important question is whether the magnetic ion is incorporated into the NC or resides on the surface. The 113Cd MAS-NMR of NCs of Cd0.991Co0.009S with diameters from 3.5 to 29.5 nm showed peaks shifted by electron hyperfine interactions from next-nearest neighbor Co2+ ions, and by comparison with results from bulk samples that were discussed in Sect. 3.5 it was concluded that Co2+ ions occupied Cd2+ sites and were distributed homogeneously ... 

Magnetic defects can be thought of as defects in the magnetic dipole state of an atom or group of atoms compared to those of the parent structure. For instance, magnetic defects can be considered to form when magnetic ions are introduced into a nonmagnetic structure, either as substituents or as interstitials (Fig. 9.1a and 9.1b). These... 

The interaction between a charged point defect and neighboring magnetic ions in magnetically doped thin films has been described in terms of a defect cluster called a bound magnetic polaron (Fig. 9.5a). The radius of a bound magnetic polaron due to an electron located on the defect, r, is given by... 

Figure 9.5 Schematic representation of a bound magnetic polaron (a) one bound magnetic polaron located on a charged defect and (b) overlapping bound magnetic polarons leading to ferromagnetic alignment of magnetic ions.

In the simplest case in which the trivalent Fe-57 ions are completely incorporated into the cooperative antiferromagnetic system of the bulk substrate, the Fe-57 ions are expected to align parallel or antiparallel to the magnetic ions of the substrate in a similar manner as the ferric ions of the substrate. When the trivalent Fe-57 ions are on the surface, however, their magnetization is considered to be reduced to some extent due to reduction in the number of neighboring magnetic metal ions interacting with them. 

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