Interaction indirect RKKY

The canonical spin glass consists of a noble metal (Au, Ag, Cu, or Pt) diluted with a transition metal ion, such as Fe or Mn. The magnetic interaction in such systems is mediated by the conduction electrons, leading to an indirect exchange interaction—the RKKY (Ruderman and Kittel [70], Kasuya [71], and Yosida [72]) interaction, whose coupling constant J R) oscillates strongly with distance r between the spins as... 

It was shown in section 3 that the transport properties of magnetic R-non-transition metal compounds can be understood in terms of a direct exchange interaction between conduction electrons and R localized moments. This interaction leads to an indirect RKKY interaction between the localized moments which describes the magnetic properties of these compounds. 

Here Xt is the static susceptibility of the f-electron system, E is the magnetic relaxation rate of the f-state and Kff denotes the coupling constant of the spin of the ESR probe to the f moment via the indirect RKKY exchange. A schematic representation of the interactions which are described in eq. (34) and are responsible for the linewidth broadening in HFS is shown in fig. 41. 

We have clearly demonstrated electronic influences on structure due to indirect interactions. In non-magnetic alloys, electric polarization of the electron cloud around localized charges (ions) causes Friedel oscillations and hence a preferred position of the ions. In magnetic alloys, evidence of another indirect interaction due to spin polarization around localized local moments causing RKKY oscillations has been shown. 

The behaviour pertinent to the opposite limit of the well localized f states is found in most rare-earth compounds. The 4f states are situated more than 5 eV below EF in most of them. The strength of the interaction of f and conduction-band electrons is considerable (= 0.1 eV), but contributes only indirectly to the magnetic coupling of f-moments via polarization of conduction electrons (RKKY), the 4f-moment magnitude remaining preserved. For f states closer to EF, as is the case of y-Ce or some Ce compounds (a situation comparable To some actinide compounds), the interactions between the f- and conduction-band states becomes stronger. The Kondo Hamiltonian can be written as... 

Since the B-C bonds in RB2C2 do not require any electron transfer from rare earth metals, all the rare earth diborodicarbides are expected to have three conduction electrons per formula unit. Therefore, it is reasonable to assume that the main magnetic interaction in RB2C2 is the f-f indirect exchange via conduction electrons (the RKKY interaction), as was subsequently verified by the relation of the values with the de Gennes factors (Sakai et al. 1982a). 

An ESR study of the concentration dependence of the fully narrowed resonance linewidth in the hexaborides M jEui cB6 (M=Sr or La) in a wide concentration range 0exchange between Eu -ions is due to the presence of free carriers (indirect exchange via the RKKY-interaction), although a straightforward application of the RKKY-theory gives only qualitative agreement with the experimentally observed AH x) curves. In the lanthanum compoimds, the concentration dependence of... 

---