Ferromagnetic phase transition

In this talk we d like to address magnetic properties of quark matter at low temperature. We first discuss the ferromagnetic phase transition and then a pos-... 

Ac-susceptibility measurements on (Ga,Mn)As with x = 0.042 have been performed in alternating B from 0.1-4 mT. In the temperature dependence of susceptibility, there is a sharp peak at about 48 K at 0.1 mT, which suggests a ferromagnetic phase transition. The temperature and magnetic field dependence is rather complicated and an increase of B involves additional peaks (the number of which up to 4), which may be due to domain formation and domain wall movement (Sadowski et al. 2000). There is also a report about ac-susceptibility measurements on (Ga,Mn)As with x = 0.07, which shows that there is no difference between the field-cooled and zero-field cooled ac-susceptibilities measured with B = 10 mT (Van Esch et al. 1997). 

Eu MnSbn was reported to be an intermetallic colossal magnetoresistive material having a metal insulator transition associated with a ferromagnetic phase transition at 92 K (Chan et... 

This nonequilibrium phase diagram is in the form of a cusp in (m,t,h) space (see Ref. 45 for definitions). It is a perfect analogue of a ferromagnetic phase transition if we interpret m,t,h as magnetization, temperature (minus its critical value), and applied magnetic... 

Equation (2) describes a paramagnetic to ferromagnetic phase transition at = NppoAlk. A similar calculation for atoms with J > 1/2 can be performed by summing over each of the U + 1) magnetization states. The result is that the tanh function in Equation (2) is replaced by the Brillouin function (see any textbook of solid state physics, e.g. Kittel 1976 or Crangle 1977). 

Fig. 2.43 The temperature dependence of low-field magnetization (B = mT) for three multilayer structures LuS-PbS on Bap2 substrate. Circles correspond to LuS(3 ML) - PbS(50 ML), triangles to LuS(4 ML) - PbS(51 ML) and squares to LuS(16 ML) - PbS(51 ML). The arrows point on the ferromagnetic phase transition temperature Tc determined as inflection point of M T) curve [70]...

With respect to the fact that the extrapolation length is proportional to the gradient coefficient (4.43a), its renormalization due to the flexoeffects should also be taken into account. Sometimes it may lead to the disappearance of the size-induced ferroelectric/ferromagnetic phase transition [77]. 

Magnetic properties of 03807 and 07805 are similar. The dependences x T) indicate an anti ferromagnetic phase transition at 5.1 K and 2.9 K, respectively (Boucherle et al. 1987, 1989). In accordance with these data the el atoms, which are similar to e atoms in eSo3, are in the state of intermediate valence, and the e2 atoms have the valence value equal to three. Two kinds of e atoms have different magn c properties the el atoms are nonmagnetic, and the e2 atoms are the carriers of the magnetic properties. 

CeMnSna and 7 c = 520K for CeMno.sSna- The xiT) dependence of the Ce compounds follow the Curie-Weiss law above the Tq points, and the xiT) dependences of the LaMni 2(Sn2 y, PrMni jSna-, NdMni-j Sna-, and SmMni Sna- - compounds obey the Curie-Weiss law above the liquid nitrogen temperature. The Pr, Nd and Sm compounds undergo an anti ferromagnetic phase transition at low temperatures. 

In fig. 17.33 it is demonstrated how the zone-center modes behave as function of temperature especially as one goes through the ferromagnetic phase transition. Approaching from above one notices that the A-A transition does not become soft due to the elastic processes within the triplets. 

Calculation of the physical properties of a spatially uniform, macroscopic system requires information about f[(y,T] only in the immediate vicinity of its minimum at temperature T, due to the sharpness of the peak in the function exp —j8V/[(7,T] (See Appendix A). This implies that for a physical system having a second-order phase transi-ton at T = Tc, with a = 0 for T > Tc and (r 7 0 for T < Tc (such as the ferromagnetic phase transition), many features of the transition can be deduced if /[finite values when evaluated at (t = 0, T = Tc. For a second-order phase transition the value of [Pg.150]

Zheludev, A., Ressouche, E., Schweizer, J., Turek, R, Wan, M., and Wang, H., Neutron diffraction observation of a ferromagnetic phase transition in a purely organic crystal. Solid State Commim., 90, 233, 1994. 

A. Caneschi, D. Gatteschi, J. P. Renard, P. Rey, and R. Sessoli, Ferromagnetic phase transitions of two one-dimensional ferrimagnets formed by manga-nese(ll) and nitronyl nitroxides cis octahedrally coordinated, Inorg. Chem., 28, 3314 (1989). 

Rie] Ried, K., Kohler, D., Kronmuller, H., Experimental Hints for Crossover-Behavior in the Ferromagnetic Phase-Transition of Fei4Nd2B , J. Magn. Magn. Mater., 116, 259-266 (1992) (Phase relations. Experimental, Magn. Prop., 33)... 

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