Magnetically aligned polycrystalline dysprosium as ultimate saturation ferromagnet for high magnetic field polepieces

Stepankin, V.

doi:10.1016/0921-4526(94)01059-a

Cited by 17 publications

(12 citation statements)

References 2 publications

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“…3). A dysprosium single crystal, oriented with the applied field parallel to the easy axis of magnetisation, would have a fully saturated induction of 3.6 T at fields well below 1 T. 26 We are now replacing our polycrystalline dysprosium with a single crystal of the same dimensions 38 and expect to obtain an improved sensitivity of better than 1.8 × 10 −14 J/T for the isotropic magnetisation, which is, moreover, independent of the applied magnetic field above ∼0.5 T.…”

Section: Discussion and Perspectivesmentioning

confidence: 99%

“…We used dysprosium (Dy) for our ferromagnetic material, due to its extremely high saturation induction of ∼3.6 T. 26,27 The bar of 0.5 × 0.5 × 1.0 mm 3 was made by clamping together five 0.5 × 1.0 mm 2 pieces of 0.1 mm thick Dy foil. 28 The bottom surface of the bar, the surface closest to the sample, was polished to ensure that it was perfectly flat.…”

Section: Design Of the Magnetometermentioning

confidence: 99%

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High sensitivity magnetometer for measuring the isotropic and anisotropic magnetisation of small samples

McCollam

Rhee

Rook

et al. 2011

Review of Scientific Instruments

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We describe how the full, isotropic and anisotropic, magnetisation of samples as small as tens of micrometers in size can be sensitively measured using a piezoresistive microcantilever and a small, moveable ferromagnet. Depending on the position of the ferromagnet, a strong but highly local field gradient of up to ∼4200 T/m can be applied at the sample or removed completely during a single measurement. In this way, the magnetic force and torque on the sample can be independently determined without moving the sample or cycling the experimental system. The technique can be used from millikelvin temperatures to ∼85 K and in magnetic fields from 2 T to the highest fields available. We demonstrate its application in measurements of the semimagnetic semiconductor Hg 1−x Fe x Se, where we achieved a moment sensitivity of better than 2.5 × 10 −14 J/T for both isotropic and anisotropic components.

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Section: Discussion and Perspectivesmentioning

confidence: 99%

Section: Design Of the Magnetometermentioning

confidence: 99%

High sensitivity magnetometer for measuring the isotropic and anisotropic magnetisation of small samples

McCollam

Rhee

Rook

et al. 2011

Review of Scientific Instruments

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“…Therefore we have chosen to use Dy as magnetic material, because it has a very high saturation magnetization (about 3.2 T), which is already reached at relatively low fields (`5 T) [5]. To increase the magnetic moment of the 2D excitons we have chosen a QW of CdMnTe, of which the lowest exciton level shows a large downward energy shift with increasing magnetic field, due to the exchange interaction of the excitons and the Mn ions [6].…”

Section: Experimental Geometrymentioning

confidence: 99%

Two-Dimensional Excitons in Large Magnetic Field Gradients

Pulizzi

Christianen

Maan

et al. 2000

phys. stat. sol. (a)

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Inhomogeneous magnetic fields are used to exert a magnetic force on two-dimensional excitons. The large field gradients are produced by positioning a thin magnetized stripe of dysprosium on top of a semi-magnetic CdMnTe/CdMgTe quantum well. By measuring the photoluminescence energy and intensity, spatially resolved with mm resolution, the actual value of the local magnetic force, which can be as high as 0.4 meV/mm, and its effect on the exciton motion are determined.Introduction Spatially inhomogeneous magnetic fields have been frequently used to control the motion of electrically neutral physical systems, like atoms and molecules. One important example is the use of a magnetic trap to confine atomic gases to a limited region of space, which recently has permitted the observation of Bose-Einstein condensation [1]. The underlying trapping mechanism stems from the fact that in a given magnetic field gradient rB an object with a certain magnetic moment m, experiences a magnetic force F given by F mrB. Recently it has been shown that this magnetic force even can be used to trap diamagnetic biological tissue, including living creatures as frogs or grasshoppers [2], or ferromagnetic objects [3].Inspired by these studies we want to explore the possibility to magnetically confine excitons in semiconductor heterostructures. Therefore we study the effect of the magnetic force on two-dimensional (2D) particles in a semiconductor quantum well (QW), where the thin layer restricts the longitudinal and the magnetic force the lateral movement. In a nonmagnetic QW all particles, i.e. electrons, holes and bound electron±hole pairs (excitons), exhibit a diamagnetic response to an external magnetic field, which means that they all are driven to the same region of space where the field is lowest. In this sense using magnetic forces to spatially confine excitons is fundamentally different from its electrostatic counterpart [4], where the electric force is opposite for electrons and holes, driving them apart. In order to realize the field gradients strong enough to control the motion of excitons it is necessary to vary the field considerably (few Tesla) on a distance comparable to the typical exciton diffusion lengths (few mm).In this paper we demonstrate how to produce such field gradients by positioning a thin magnetized dysprosium (Dy) stripe directly on top of a QW, and how to measure this gradient and its effect on the exciton motion by using spatially resolved photoluminescence (PL) and PL-excitation (PLE) spectroscopy.

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“…Locally, the crystal field and anisotropic ion interaction leads to a large magnetic anisotropy that can only be overcome by very high magnetic fields, perhaps hundreds of Tesla. Thus although it is possible to saturate a single crystal of Dy by applying fields $ 1 T along the a axis of the hcp crystal structure [2], polycrystalline films require fields of $ 50 T to produce saturation [3]. For technological applications effort has been applied to producing polycrystalline Dy with magnetically aligned crystallites and saturation has been demonstrated in magnetically aligned polycrystalline Dy at a field $ 6 T at 4.2 K [3].…”

Section: Introductionmentioning

confidence: 97%