Antiferromagnetic ordered state

In agreement with the overall behaviour of the / Ni2B2C compounds with heavy 4f elements R, shown in fig. g, this compound is the unique member of the / Ni2B2C series in which the onset of superconductivity takes place in an antiferromagnetically ordered state i.e. jTn — 11 K>7 C = 6.3K (also see table 7). It should be noted that in the ruthenocuprates discussed in subsection 1.3 also antiferromagnetic order (and even... 

Figure 5 The generic phase diagram of the (TMfjX as a function of pressure or anion substitution. On the left, the normal phase of sulfur compounds can be described as a Luttinger liquid that becomes gapped in the charge sector (LL, ) below Tj, and can develop either a spin-Peierls (SP) or localized antiferromagnetic ordered state. Under pressure, the properties of the sulfur series evolve toward those of the selenides for which the normal state shows a progressive restoration of a Fermi liquid (FL) precursor to antiferromagnetism (AF) and superconductivity (S), after [28].

Mossbauer spectroscopy was applied to heavy fermion superconductors of UPd2Al3, URu2Si2, and UPt3. A common feature in these compounds is the observation of paramagnetic relaxation. However, the observation of the hyperfine field in their antiferromagnetic ordered states is different among them. The conclusions of the application of the Mossbauer spectroscopy to the heavy fermion superconductors are as follows ... 

An actual divergence in x Q) at some value Q occurs for an antiferromagnetically ordered state in which the electron spin orientations oscillate with a wavelength A = 2ir/j2o-... 

The hexaborides for which the oxidation state of the metal is 2 -f- are CaB, SrBg, BaB5, EuB, YbB. They are diamagnetic except EuB, which is ferromagnetic (Tc = 12.5 K) . The other rare-earth hexaborides are characterized by the 3-1-oxidation state, except for SmB, in which samarium is in a mixed valence state. They exhibit antiferromagnetic order at low T except LaB, YB and SmB . ... 

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. 

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