Antiferromagnetic resonance Antiferromagnetism

Luis, F., Del Barco, E., Hernandez, J.M., Remiro, E., Bartolome, J., and Tejada, J. 1999. Resonant spin tunneling in small antiferromagnetic particles. Physical Review B 59 11837-11846. 

When I J is of the order of hundreds of wavenumbers, i.e., it is of the order of kT, then the excited S levels are not fully populated. In homodimers antiferromagnetically coupled, the ground state is diamagnetic (S = 0). If only one metal ion is sensed by the resonating nucleus, nuclear relaxation... 

Paramagnetic resonance has been observed in a-Cr203 above the antiantiferromagnetic Curie point by Maxwell and McGuire (171) antiferromagnetic resonance has been studied in a-CraOj by Dayhoff (172). 

Fia. 33. Paramagnetic resonance of a-chromia at various temperatures. The antiferromagnetic Curie point is approximately 30 173). 

The six high spin Fe sites in the [(Fe6S5X5)(M(CO)3)2]" anions are antiferromagnetically coupled as evidenced by the reduced ambient temperature magnetic moments, and the temperature dependence of the isotropically shifted resonances in the aryloxide derivatives. 

Minkiewicz, V., and A. Nakamura Direct observation of Mn nuclear magnetic resonance in antiferromagnetic CsMnFj. Phys. Rev. 143, 361 (1966). 

Ito H, Kondo T, Sasaki H, Saito G, Ishiguro T (1999) Antiferromagnetic spin resonance and magnetic phase diagram of deuterated /c-(BEDT-TTE)2Cu[N(CN)2]Br. Synth Met 103 1818-1819... 

Because the iron ions carry a magnetic moment, the Hall data are difficult to interpret. The conventional theory of the Hall effect utilizes a spin-independent resonance (transfer-energy) integral, and an adequate theory incorporating a spin-dependent resonance integral needs to be developed for antiferromagnetic materials. 

A further non-metallic state without antiferromagnetic order is that with resonating valence bonds , proposed by Anderson (1987). This has been described in Chapter 3. 

The electron gas thus obtained, though nearly antiferromagnetic , has no antiferromagnetic order. It is called highly correlated" because only some 10% or less of the atomic sites contain two (or no) electrons the others each contain one electron, of which the spin is resonating between the two possible positions. This behaviour is illustrated in Fig. 4.6. 

Next, we discuss the magnetic behaviour of the materials described here as B/U is varied. The moment at T=0 in the antiferromagnetic lattice and Goodenough s (1971) conjecture for the Neel temperature are shown in Fig. 4.12. There exists at present no good theoretical description of the way TN drops as we go towards the value of B/U where the moments vanish. Near this value we do not expect an entropy /cBln 2 on going through the Neel point. With small values of there is a quantum-mechanical resonance between the two directions of the moment, and the moments on a given atom are nearly equal, so < z> is small at TN they become equal. The susceptibility should appear as in Fig. 4.13. 

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