Magnetism of YMn6Sn6 and DyMn6Ge6: Single-crystal Study
The magnetic properties of YMn6Sn6 and DyMn6Ge6, which crystallize in the hexagonal HfFe6Ge6-type of structure, have been studied on single crystals that have been prepared in an Sn flux and In flux, respectively. The compounds order antiferromagnetically at about 330 K and 450 K and exhibit very complex magnetic properties in the magnetically ordered state. The evolution of the magnetization in the ordered state has been investigated in the temperature region from 2 to 550 K and magnetic field up to 14 T.
UvA-DARE ( Digital Academic Repository ) A Neutron Diffraction Study of the Magnetic Ordering of HoMn 6 Ge 6
The hexagonal compound HoMn6Ge 6 of HfFe6Ge6-type of structure (P6/mmm) orders antiferromagnetically below TN = 466 K and undergoes a second magnetic transition at T t = 200 K. Neutron powder diffraction has shown that the low-temperature phase is a triple skewed spiral with wave vector ql = (0, 0, qz), consisting of ferromagnetic Ho and Mn layers coupled almost antiparallel in a three-layer sequence: Mn( + ) H o ( )-Mn( + ). The plane of the moments is rotated about an axis in the hexagonal plane so that its normal makes a nonzero angle with ql. This structure may be regarded as a combination of an elliptic helix with a longitudinal wave with the same wave vector. The wave vector length is incommensurate with the crystal lattice and is temperature dependent, at 9 K qz = 0.1979(2) r.l.u., which corresponds to an interplanar turn angle of ~s = 71-24° in the direction of ql. Above T t = 200 K a spin reorientation transition, associated with a decoupling of the Mn and Ho sublattices sets in, and the skewed spiral structure gets destabilised. In the transition region 200-260 K the magnetic ordering is described as a superposition of two Fourier coefficients/atom, associated with the wave vectors ql = (0, 0, q~) and q2 = (0, 0, 1/2) corresponding to a distorted spiral with fluctuating Mn moment values and directions. The H + ql satellites (skewed spiral) comprise Ho as well as Mn contributions, while the H + q2 comprise only the Mn antiferromagnetic ordering along c. Above 260 K the ordering consists exclusively of the H + q2 Mn intensity contributions.
Comparison between Two Chemicals for Reducing Scale Formation in Reverse Osmosis Systems
In this present research was transacted with the calcium carbonate scale inhibition on the membrane surface of the reverse osmosis desalination system. Influence of changing feed solution flow rate (10-25)l/h, pH of the feed solution (6-10) on the recovery ,penetrate flow rate and total dissolved solid in (RO) system by using solution of calcium carbonate as feed solution was investigated, furthermore the effect of adding two types of scale inhibitor ,zinc chloride and polyamino polyether methylene phosphonate with difference concentration (2-8)mg/l for zinc chloride and (8-15) mg/l for polyamino polyether methylene phosphonate was calculated. The results showed that the permeate rate increases as the feed flow rate augmentation ,while it reducing with time, the total dissolved solids decreases as the feed flow rate increases while it increases with time and recovery rate decreases as the feed flow rate increases and it also decreases with time. It was concluded that the permeate rate decreases as the feed solution pH value increases and it cause high scale forming thus decrease the permeate TDS.By adding the scale inhibitor, it was found that the permeate rate and recovery rates increases as the concentration of inhibitor increases while the total dissolved solids decreases in the permeate with increasing the concentration of both inhibitors .It was discovered that Polyamino polyether methylene phosphonate more sturdy than zinc chloride as scale inhibitor for reverse osmosis desalination system in all concentrations was studied in this article.