M.A. Semary

Field dependence of the susceptibility maximum for two-dimensional antiferromagnet

Abstract The magnetic susceptibility measurements on layered type structure ( CH 3 NH 3 ) 2 FeCl 2 Br 2 revealed a transition temperature T N ( H = 0) ≈ 100 K . The transition temperature of ( CH 3 NH 3 ) 2 FeCl 4 was previously found to be T N ( H = 0) ≈ 95 K . The effect of magnetic field on the transition temperature and peak intensity for both compounds has been investigated.

Magnetic susceptibility investigation of some antiferromagnetic Fe2+ complexes

Abstract The magnetic susceptibility of (C n H 2n+1 NH 3 ) 2 FeCl 4 , where n = 1, 2, 3, 4 and [(CH 3 ) 2 NH 2 ] 2 FeCl 4 , is measured in the temperature range 80–300 K. The results are interpreted in terms of a canted 2-dimensional antiferromagnet that approximates the X − Y model. The effect of varying the magnetic field strength on the susceptibility behaviour is discussed.

Magnetic history of hexanediammonium tetrachloroferrate(II)

Abstract The magnetic susceptibility of the two-dimensional antiferromagnet (CH 2 ) 6 (NH 3 ) 2 FeCl 4 is reported. The compound has unusual dependence on its magnetic history below its Neel temperature T N . Though the magnetic ordering is associated with a structural distortion, this distortion does not seem to explain the magnetic behaviour of the compound. The results have been interpreted in terms of mixed magnetic phases which are likely to exist when the sample is cooled in a magnetic field.

Magnetic studies of the layered compounds (CH2)n(NH3)2FeCl4, n = 2, 3 and 6

Abstract The magnetic susceptibility as a function of temperature and field strength of the series of compounds (CH2)n(NH3)2FeCl4, n = 2, 3 and 6 have been investigated. The three compounds undergo magnetic transitions at TN(H = 0) = 105.0±1, 94.5+0.5 and 98.0+0.5 K. From the susceptibility and DTA measurements no evidence for structural phase changes is found in the investigated temperature range. The results are interpreted in terms of a canted antiferromagnetic arrangement. With increasing n the interlayer spacing increases and the magnetic structure becomes more and more two dimensional.

Magnetic susceptibility studies of (CH2)3(NH3)2FeCl2Br2 and (CH2)6(NH3)2FeCl2Br2

Abstract The magnetic susceptibility of the layered compounds (CH 2 ) 3 (NH 3 ) 2 FeCl 2 Br 2 and (CH 2 ) 6 (NH 3 ) 2 FeCl 2 Br 2 has been measured in the range 80 T T T

On two types of creep behaviour of CuZn solid solution

Abstract The stress and temperature dependence of steady state creep rate is investigated for Cu-30%Zn and Cu-10%Zn alloys under stresses of 15–40 kg mm−2 in the temperature range 200–325°C. The existence of a critical stress σc (T), which separates two types of behaviour characterized by a sensitivity parameter m′ close to three at low stresses and m′ > 6 for higher stresses, has been observed. It is thought that a change occurs in the mechanism which controls the creep rate. Also the investigation of transient creep gives evidence of two types of creep behaviour. It is shown that the creep of α-brasses can be described as a viscous glide of dislocations at low stresses. The shear mechanism owing to the slip of dislocation along shear planes is the mechanism controlling the creep rate at higher stresses. Zinc concentration seemed to be ineffective on the mechanisms controlling the creep rate. The values of apparent activation energy, namely 39.3 kcal mol−1 and 33.4 kcal mol−1 for Cu-10%Zn and Cu-30%Zn alloys respectively, show that the creep is controlled by self-diffusion.

High-temperature susceptibility of copper compounds containing CuCl2-4 or Cu2Cl2-6 ions

We have measured the magnetic susceptibility of [(C2H5)2NH2]2 CuCl4, (iso-C3H7NH3)2CuCl4, and (iso-C3H7NH3)CuCl3 in the temperature range 80 < T < 400 K. These compounds show thermochrimic first order phase transitions at 315.5, 329.5 and 324.5 K, respectively, which is related to the change in geometry of the chlorine coordination of Cu2+. From the susceptibility data, estimates of the super-exchange interaction can be inferred. For [(C2H5)2NH2]2CuCl4 and (iso-C3H7NH3)2CuCl4 our results evidenced the presence of ferromagnetic interactions between the Cu ions within the network formed by CuCl2-4 ions. For the (iso-C3H7NH3)CuCl3 the interaction between two Cu2+ ions forming the dimer can be estimated. The interaction between the dimers is found to be much weaker.