Magnetic domain formation in itinerant metamagnets

We examine the effects of long-range dipolar forces on metamagnetic transitions and generalize the theory of Condon domains to the case of an itinerant electron system undergoing a first-order metamagnetic transition. We demonstrate that within a finite range of the applied field, dipolar interactions induce a spatial modulation of the magnetization in the form of stripes or bubbles. Our findings are consistent with recent observations in the bilayer ruthenate Sr$_3$Ru$_2$O$_7$.Comment: 4 pages, 3 figures, minor changes, references adde

Letter from H. B. Simons to Hubert Creekmore

Simons writes from Palestine, Texas, to Creekmore, regarding The Chain in the Heart. He expresses his surprise at learning that Creekmore is not African American, and he praises Creekmore for understanding African Americans\u27 experiences in the South at the time.https://egrove.olemiss.edu/creekmore/1176/thumbnail.jp

Barkhausen noise from zigzag domain walls

We investigate the Barkhausen noise in ferromagnetic thin films with zigzag domain walls. We use a cellular automaton model that describes the motion of a zigzag domain wall in an impure ferromagnetic quasi-two dimensional sample with in-plane uniaxial magnetization at zero temperature, driven by an external magnetic field. The main ingredients of this model are the dipolar spin-spin interactions and the anisotropy energy. A power law behavior with a cutoff is found for the probability distributions of size, duration and correlation length of the Barkhausen avalanches, and the critical exponents are in agreement with the available experiments. The link between the size and the duration of the avalanches is analyzed too, and a power law behavior is found for the average size of an avalanche as a function of its duration.Comment: 11 pages, 12 figure

Magnetization reversal and anomalous coercive field temperature dependence in MnAs epilayers grown on GaAs(100) and GaAs(111)B

The magnetic properties of MnAs epilayers have been investigated for two different substrate orientations: GaAs(100) and GaAs(111). We have analyzed the magnetization reversal under magnetic field at low temperatures, determining the anisotropy of the films. The results, based on the shape of the magnetization loops, suggest a domain movement mechanism for both types of samples. The temperature dependence of the coercivity of the films has been also examined, displaying a generic anomalous reentrant behavior at T$>$200 K. This feature is independent of the substrate orientation and films thickness and may be associated to the appearance of new pinning centers due to the nucleation of the $\beta$-phase at high temperatures.Comment: 9 pages, 7 figure

Stream Reaeration in Nonuniform Flow: Macroroughness Enhancement

The authors presented two papers that are a welcome addition to the topic of water quality and stream reaeration. The renewal theory and small eddy model provide interesting results for smooth and small-roughness channels. The discussers feel, however, that the second paper highlights some limits of the method, particularly when free-surface aeration takes place. The present discussion provides additional material on the problem of stream reaeration in the presence of 'whitewater' (i.e., air bubble entrainment). It complements the original paper, and some references are added, including large-scale data

Induced Anisotropies in NiCo Obliquely Deposited Films and Their effect on Magnetic Domains

English Article: Oblique and in-plane anisotropies in obliquely evaporated NiCo thin films were investigated in order to understand their origin. All the compositions studied clearly show the effect of columnar grain morphology coupled with some intrinsic factors such as magnetostriction and crystallinity. Energy calculations are undertaken to explain the effect of

Domain walls in (Ga,Mn)As diluted magnetic semiconductor

We report experimental and theoretical studies of magnetic domain walls in an in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our high-resolution electron holography technique provides direct images of domain wall magnetization profiles. The experiments are interpreted based on microscopic calculations of the micromagnetic parameters and Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial and biaxial magnetocrystalline anisotropies in the film is directly reflected in orientation dependent wall widths, ranging from approximately 40 nm to 120 nm. The domain walls are of the N\'eel type and evolve from near-$90^{\circ}$ walls at low-temperatures to large angle [1$\bar{1}$0]-oriented walls and small angle [110]-oriented walls at higher temperatures.Comment: 5 pages, 4 figure

A smooth cascade of wrinkles at the edge of a floating elastic film

The mechanism by which a patterned state accommodates the breaking of translational symmetry by a phase boundary or a sample wall has been addressed in the context of Landau branching in type-I superconductors, refinement of magnetic domains, and compressed elastic sheets. We explore this issue by studying an ultrathin polymer sheet floating on the surface of a fluid, decorated with a pattern of parallel wrinkles. At the edge of the sheet, this corrugated profile meets the fluid meniscus. Rather than branching of wrinkles into generations of ever-smaller sharp folds, we discover a smooth cascade in which the coarse pattern in the bulk is matched to fine structure at the edge by the continuous introduction of discrete, higher wavenumber Fourier modes. The observed multiscale morphology is controlled by a dimensionless parameter that quantifies the relative strength of the edge forces and the rigidity of the bulk pattern.Comment: 4 pages, 4 figure

Direct observation of domain wall structures in curved permalloy wires containing an antinotch

The formation and field response of head-to-head domain walls in curved permalloy wires, fabricated to contain a single antinotch, have been investigated using Lorentz microscopy. High spatial resolution maps of the vector induction distribution in domain walls close to the antinotch have been derived and compared with micromagnetic simulations. In wires of 10 nm thickness the walls are typically of a modified asymmetric transverse wall type. Their response to applied fields tangential to the wire at the antinotch location was studied. The way the wall structure changes depends on whether the field moves the wall away from or further into the notch. Higher fields are needed and much more distorted wall structures are observed in the latter case, indicating that the antinotch acts as an energy barrier for the domain wal

Effect of Total Dissolved Solids and Sulfates in Drinking Water for Growing Steers

A study was conducted to determine the effects of implants and transportation on the metabolic status of feedlot steers. Steers (n = 28) were sorted by body weight, allocated into light or heavy blocks, and randomly assigned to one of two treatments. Treatments included non-implanted controls (CON) and steers implanted with Synovex Plus 70 d prior to harvest (IMP). Jugular blood and muscle biopsy samples (longissimus dorsi (LD) and semimembranosis (SM)) were collected 70 d post-implant, prior to transit. Steers were transported to Schuyler, NE, where blood and biopsy sampling was repeated. After harvest, carcass data were collected and muscle samples were taken from the LD, SM, Psoas Major (PM), and Illiacus (IL) muscles. Implanting increased (P \u3c 0.05) estradiol levels and improved live animal performance. Carcass weight and rib eye area were increased (P \u3c 0.05) in implanted steers. No dark cutters were found in either treatment. Pre-transit insulin/glucagon ratio and muscle glycogen levels did not differ (P \u3e 0.10) between treatments. Non-esterified fatty acid (NEFA) levels were reduced (P \u3c 0.05) in implanted steers pre-transit. Transit increased (P \u3c 0.05) NEFA levels, but had no effect (P \u3e 0.10) on insulin/glucagon ratio or muscle glycogen levels. Implanting did not affect (P \u3e 0.10) insulin/glucagon ratio, NEFA, or LD glycogen levels post-transit. Implanted steers had lower (P \u3c 0.05) glycogen levels in the SM than did non-implanted steers post-transit. Weight block affected (P \u3c 0.05) insulin and insulin/glucagon ratio levels, with steers in the light block having greater levels of each. Muscle pH and objective color (L*, a*, b*) of the LD were not biologically different between treatments. Implanted steers had greater (P \u3c 0.05) glycolytic potential values in the LD, and tended (P \u3c 0.10) to have higher L* values in the PM. Implanting increased (P \u3c 0.05) shear force of the LD. These data indicate that although implants affect bovine metabolism, other factors are necessary to cause a sufficient reduction in muscle glycogen and to produce a dark cutting carcass