NMR of colossal magnetoresistive manganites and expanded lattice intermetallics at high pressure

A survey is given of NMR studies of colossal magnetoresistive manganese per ovskites (R-E,Ca,Sr,Ba)MnO3 (RE = rare earth) and the interstitially modifi ed permanent magnet materials, RE(2)Fe(17)A(x) (A = N,C,H) at ambient press ure and at applied pressures of up to 10 kbar. The different pressure behav ior of the Mn hyperfine field found in the metallic and in the insulating m anganite compounds is discussed and related to the micro- and macroscopic p roperties of these magnetically inhomogeneous materials. In the RE2Fe17Ax c ompounds a different pressure behavior of the hyperfine field at the RE sit es with different number and type of interstitial atom neighbors is discuss ed in terms of local compressibility. The influence of the interstitial mod ification and the applied pressure on the RE hyperfine field and quadrupole splitting is analyzed and the impact of the "chemical pressure" and covale nt effects on these quantities is compared. A comparison of the behavior of the magnetic state of the 4f electron shell with pressure and with interst itial modification is made and the relation to the magnetocrystalline aniso tropy is discussed.