Diamagnetic behavior

The second salt presents a structure where the anions occupy the tunnels formed by BEDT-TTF dimers. BEDT-TTF bears the unit positive charge. This salt behaves like a semiconductor with a very low room-temperature electric conductivity. The unpaired electrons on the organic cation-radicals are strongly antiferromagnetic coupled, giving rise to a diamagnetic behavior of the second salt, because the nitroprusside anion is also diamagnetic. 

This is consistent with the result that Horowitz et al. have found on submicron particles obtained by a hyponitrite method they are too small to give any diamagnetic behavior. However, the heat capacity measurement shows a break at 90 K that corresponds to about 90% of superconducting phase in the powder (16). 

The diamagnetic behavior of the diiron and tetrairon complexes, despite the presence of formally d1 and/or d9 iron centers, indicates very strong coupling between the individual paramagnetic centers all theoretical treatments of polynuclear iron-sulfur-nitrosyl complexes to date have been based on the assumption of diamagnetism in even-electron species and have employed molecular orbital methods at various levels of approximation. 

FIG. 2. (Color online) (a) TEM image of A1203 nanoparticles heated at 500 C and (b) their magnetization curves showing ferromagnetism even at 390 K. Note that the nanoparticles sintered at 1400 °C exhibit diamagnetic behavior at 300 K. 

Superconducting materials have been known since the discovery of the phenomenon of superconductivity in 1911 by Kamerlingh Onnes. They are characterized by the absence of any measurable resistivity and by their perfect diamagnetic behavior below... 

There is an upper limit to the strength of the magnetic field that can be applied to a superconductor without changing its diamagnetic behavior. At a critical field the magnetization goes toward zero and the material reverts to its normal state. For most elemental superconductors M rises in magnitude up to Her and then abruptly drops to zero this is Type I behavior. 

If the diamagnetic behavior of matter could be completely explained by local currents around the nuclei, and if the diamagnetic susceptibility of the different nuclei of the periodic table were known, the susceptibility of molecular compounds consisting of different elements would be the sum of the individual contributions, and could be easily predicted. As early as 1919, Pascal [23], and later Pacault [24] and Haberditzl [25], published simple increment systems to calculate diamagnetic susceptibilities of molecules. The increment system is quite accurate for most organic and inorganic compounds, with a few exceptions. 

Felner (1975) reported the existence of YAu2Si2 with the ordered ThCr2Si2-type of structure (X-ray powder analysis) sample preparation as for LaAu2Si2- The crystallographic data were given as I4/mmm, a = 4.230 and c= 10.18. From susceptibility measurements diamagnetic behavior was observed for a temperature range of 4.2 K to 300 K. 

Note that the paramagnetic or diamagnetic behavior of atoms is a consequence of the quantization of electron spin and the Pauli exclusion principle, both of which are purely quantum-mechanical phenomena. Thus, the experimental observation of the magnetic behavior of atoms (paramagnetic or diamagnetic) represents further experimental confirmation of the quantum-mechanical nature of atoms and molecules. 

---