A permanent magnetic film atom chip for Bose–Einstein condensation

Abstract

Abstract.We present a hybrid atom chip which combines a permanent magnetic film with a micromachined current-carrying structure used to realize a Bose-Einstein condensate. A novel TbGdFeCo material with large perpendicular magnetization has been tailored to allow small scale, stable magnetic potentials for ultracold atoms. We are able to produce 87 Rb Bose-Einstein condensates in a magnetic trap based on either the permanent magnetic film or the current-carrying structure. Using the condensate as a magnetic field probe we perform cold atom magnetometry to profile both the field magnitude and gradient as a function of distance from the magnetic film surface. Finally we discuss future directions for our permanent magnetic film atom chip.

Permanent magnetic lattices for ultracold atoms and quantum degenerate gases

“…The permanent magnetic lattice configurations considered here should be suitable for trapping and manipulating small clouds of ultracold atoms prepared in low magnetic field-seeking states, including Bose-Einstein condensates and ultracold Fermi gases. A cloud of ultracold atoms could be loaded into the permanent magnetic lattice using, for example, a hybrid magnetic field structure comprising a current-carrying 'U' quadrupole trap and a 'Z' Ioffe-Pritchard trap located beneath the permanent magnetic array on the atom chip [15]. Such a hybrid structure should allow ultracold atoms to be initially loaded from a mirror MOT into the 'U' surface MOT, then into the 'Z' magnetic trap, and finally into the 2D magnetic lattice.…”

“…Radia was also used to test various proposed configurations of permanent magnets that might support periodic arrays of microtraps with non-zero potential minima based on symmetry arguments. Figure 1(d) shows a numerical calculation of the magnetic field versus distance in the y-direction for the central region of a single finite array of n r = 1001 rectangular magnets, using the parameters a = 1 µm, t = 0.050 µm, l x = 1000.5 µm and 4πM z = 3.8 kG (corresponding to the magnetization of our perpendicularly magnetized T b 6 Gd 10 F e 80 Co 4 magneto-optical films [13,15]) and with no bias magnetic fields. Corrugations corresponding to the third-order spatial harmonic with period a/2 [16] [see (1b) and (1c)] can be seen at distances very close (≪ a/4π) to the surface.…”

Dynamically controlled toroidal and ring-shaped magnetic traps

“…Our trapping configuration is based on magnetic micro-structures, which have been proposed and demonstrated for atom trapping both using current-carrying wires [25,26,27] and permanent magnetic structures [28,29,30]. We start from a ring-shaped magnetic quadrupole field, generated by two concentric rings of magnetized material with out-of-plane magnetization M; see Fig.…”

All-optical reversible switching of local magnetization

“…17,18 If a FG film is designed to have large coercivity and high saturation magnetization, magneticdomain patterns recorded on the film can be used as miniature optically transparent permanent magnets, e.g., in the manipulation of magnetic colloidal particles [19][20][21] and trapping of dilute gaseous samples of laser-cooled atoms. [22][23][24] In the past few years, research attention has also been paid to ultrafast magnetization phenomena in FG materials. By employing a FG film that has in-plane magnetization and essentially no domain activity, all-optical modulation of the direction of magnetization on the femtosecond time scale has been demonstrated.…”