No abstract

Understanding of the laser-induced ultrafast demagnetization dynamics is one of the most challenging and hot topics in magnetism research due to its potential applications in magnetic storage devices and the field of spintronics. Recently, a laser-induced switching of ferromagnetism, driven by a disorder–order transition on FeAl thin films, has been experimentally demonstrated. The switching of ferromagnetic ordering by ultrafast laser pulses in FeAl thin films may open new possible applications of this material such as magnetic data storage and manipulation. Since the speed of the magnetic switching of magnetic states in thin films is one of the critical parameters for these applications, here we used time resolved magneto-optical Kerr measurements to investigate the demagnetization dynamics of Fe[Formula: see text]Al[Formula: see text] thin films at room temperature. We have for the first time observed a clear transition from one-step dynamics (type I) to two-step (type II) dynamics in the same material by increasing pump laser fluence. This experimental observation may give a strong confirmation that the ultrafast demagnetization process can be treated as a thermal process and is driven by the difference between temperatures of the electron and spin systems.

No abstract

In recent years, chemical admixtures have become one of the main components of concrete alongside aggregate, cement and water. In this study, the plasticizer and the antifreeze were used. The concrete specimens (the reference concrete without an admixture, concrete with plasticizer, concrete with antifreeze and concrete with plasticizer+antifreeze) were exposed to elevated temperatures (200, 400, 550 and 700 ºC) and cooling via air and water. Water absorption, ultrasonic pulse velocity and compressive strength tests were performed on the specimens. The concrete specimens were also analyzed using X-ray diffraction. The test results indicated that at the temperatures of 550 and 700 ºC and against both of the cooling regimes the plasticizer+antifreeze concrete showed a maximum strength loss. When the air cooled specimens were examined, the lowest strength loss was this obtained for reference concrete at 550 and 700 ºC. The lowest strength loss at these temperatures for the water cooled specimens was observed in the concrete with antifreeze. After being exposed to 700 ºC and the cooling regimes, no portlandite peaks were observed in the concrete mixtures was when they were compared at with the control specimen exposed to 20 ºC in the X-ray diffraction analysis.