Tailoring Magnetic and Transport Anisotropies in Co100−x–Cux Thin Films through Obliquely Grown Nano-Sheets

The magnetic and transport properties of pulsed laser-deposited Co100−x–Cux thin films were tailored through their nano-morphology and composition by controlling for the deposition geometry, namely normal or oblique deposition, and their Cu content. All films were composed of an amorphous Co matrix and a textured growth of Cu nanocrystals, whose presence and size d increased as x increased. For x = 50, all films were superparamagnetic, regardless of deposition geometry. The normally deposited films showed no in-plane magnetic anisotropy. On the contrary, controllable in-plane uniaxial magnetic anisotropy in both direction and magnitude was generated in the obliquely deposited films. The magnetic anisotropy field Hk remained constant for x = 0, 5 and 10, Hk ≈ 35 kAm−1, and decreased to 28 and 26 kAm−1 for x = 20 and 30, respectively. This anisotropy had a magnetostatic origin due to a tilted nano-sheet morphology. In the normally deposited films, the coercive field Hc increased when x increased, from 200 (x = 0) to 1100 Am−1 (x = 30). In contrast, in obliquely deposited films, Hc decreased from 1500 (x = 0) to 100 Am−1 (x = 30) as x increased. Activation energy spectra corresponding to structural relaxation phenomena in obliquely deposited films were obtained from transport property measurements. They revealed two peaks, which also depended on their nano-morphology and composition.

Glass transitions in bituminous binders

The RILEM TC 272 PIM (Phase and Interphase behavior of innovative bituminous Materials)—TG1 Binder has initiated an inter-laboratory program investigating the phase and interphase behaviour of bituminous binders. Within the scope, four laboratories evaluated the low temperature properties of seven binders with differential scanning calorimetry (DSC). DSC has been accepted as a powerful tool to evaluate, among others, the glass transitions, Tg, monitoring the endothermic or exothermic heat flow of a material under controlled temperature conditions. There are different ways to run the test, conventional temperature linear-DSC (TL-DSC), and temperature modulation-DSC (TM-DSC). The latter has been proven as an efficient method differentiating the structural relaxation phenomena from the heat capacity. In this study, emphasis was placed on comparing the Tg measured by TL- and TM-DSC to improve the interpretation of binder glass transitions. In this study, the scope was restrained to two Polymer modified Binders (PmBs): a commercially available modified binder named PmB1 and a highly modified binder (7.5 wt% high vinyl SBS) named PmB2, were evaluated and compared with two neat bituminous binders. Based on the thermographs of the PmB2 obtained through this inter-laboratory program, it was observed that the modification by 7.5% SBS resulted in a decrease of the Tg. This reduction of Tg reflects the positive influence of SBS at low temperatures.

Non-Debye Relaxations: Two Types of Memories and Their Stieltjes Character

In this paper, we show that spectral functions relevant for commonly used models of the non-Debye relaxation are related to the Stieltjes functions supported on the positive semi-axis. Using only this property, it can be shown that the response and relaxation functions are non-negative. They are connected to each other and obey the time evolution provided by integral equations involving the memory function M(t), which is the Stieltjes function as well. This fact is also due to the Stieltjes character of the spectral function. Stochastic processes-based approach to the relaxation phenomena gives the possibility to identify the memory function M(t) with the Laplace (Lévy) exponent of some infinitely divisible stochastic processes and to introduce its partner memory k(t). Both memories are related by the Sonine equation and lead to equivalent evolution equations which may be freely interchanged in dependence of our knowledge on memories governing the process.