Magnetic structure and magnetization of z-axis helical Heisenberg antiferromagnets with XY anisotropy in high magnetic fields transverse to the helix axis at zero temperature

A helix has a wavevector along the z axis with the magnetic moments ferromagnetically-aligned within xy planes with a turn angle kd between the moments in adjacent planes in transverse field Hx = 0. The magnetic structure and x-axis average magnetization per spin of this system in a classical XY anisotropy field HA is studied versus kd, HA, and large Hx at zero temperature. For values of HA below a kd-dependent maximum value, the xy helix phase transitions with increasing Hx into a spin-flop (SF) phase where the ordered moments have x, y, and z components. The moments in the SF phase are taken to be distributed on either one or two xyz spherical ellipses. The minor axes of the ellipses are oriented along the z axis and the major axes along the y axis where the ellipses are flattened along the z axis due to the presence of the XY anisotropy. From energy minimization of the SF spherical ellipse parameters for given values of kd, HA and Hx, four kd-dependent SF phases are found: either one or two xyz spherical ellipses and either one or two xy fans, in addition to the xy helix phase and the paramagnetic (PM) phase with all moments aligned along Hx. The PM phase occurs via second-order transitions from the xy fan and SF phases with increasing Hx. Phase diagrams in the Hx-HA plane are constructed by energy minimization with respect to the SF phases, the xy helix phase, and the xy fan phase for four kd values. One of these four phase diagrams is compared with the magnetic properties found experimentally for the model helical Heisenberg antiferromagnet EuCo2P2 and semiquantitative agreement is found.Comment: 14 pages, 8 captioned figure

Anticoagulant baiting for jackrabbit control

The jackrabbit, Lepus californicus, is properly called a hare rather than a rabbit, because the young are born fully furred and with eyes open. Hares differ from rabbits in anatomy and in the lack of burrowing, although individual hares often have a more or less regular retreat or "form" at the base of a bush or clump of grass. Jackrabbits rely upon speed and dodging to escape enemies. They live chiefly in open places, seldom inhabiting dense brush or woods. Black-tailed hares or jackrabbits are classed as game mammals by the California Fish and Game Code, but when found to be injuring growing crops or other property may be taken at anytime or in any manner by the owner or tenant of the premises. They also may be taken by employees of the Department of Food and Agriculture or by county employees when acting in their official capacities pursuant to the provisions of the California Food and Agriculture Code pertaining to pests. In recent years large roving populations of jackrabbits on airports have created serious problems to approaching aircraft. One such problem occurred at the Hayward Municipal Airport in Alameda County when jackrabbits caused a traffic hazard to approaching aircraft. The problem was compounded by domestic dogs chasing rabbits across the runways and dead rabbits being fed upon by scavenger birds such as gulls and turkey vultures