Metal treatment – Stock – Magnetic
Reexamination Certificate
2001-05-14
2003-05-06
Sheehan, John (Department: 1742)
Metal treatment
Stock
Magnetic
C148S101000
Reexamination Certificate
active
06558481
ABSTRACT:
TECHNICAL FIELD
This invention pertains to a method of controlling properties of a ferromagnetic samarium substance whereby the substance becomes suitably used as a spin-resolving device for charged particles and also pertains to a ferromagnetic material adapted to be controlled by this method and a spin-resolving device making use of the relevant properties.
TECHNICAL BACKGROUND
Magnetic substances are extensively used in various fields as permanent magnets, soft magnetic materials, and magnetic recording media. When magnetic substances are used as such materials, the magnetization or a magnetic field generated thereby, the interaction with an external magnetic field, and so on, are essentially utilized.
On the other hand, coupled with the recent researches on the particle-spin dependence of various interactions in the fields of high-energy physics, solid-state physics, and so on, an improvement of the technology to produce the spin-polarized particles or to measure the spin polarization has been desired.
In a magnetic substance, the electron spin is spatially polarized in a temperature range below a specific temperature called the magnetic transition point. Therefore, it is naturally thought that magnetic substances could be suitable materials for a spin-resolving device for charged particles.
Practically, however, magnetic substances, especially ferromagnetic ones, are rarely used in the spin-resolving technology; but instead, for example, a semiconductor excited by a circularly polarized laser beam is used as a polarized electron-beam source, and the diffraction and/or scattering of an electron beam from heavy elements such as gold, tungsten, etc., or the emission of a circularly polarized light from a GaAs film irradiated with an electron beam is used in the measurement of the spin polarization of an electron beam (see JP
08-248141
).
The main reason for the inapplicability of ferromagnetic substances to the spin-resolving device resides in the fact that the ferromagnetic ordering of the electron spin over a macroscopic range is usually accompanied with the generation of a finite magnetization. The magnetization of a ferromagnetic substance is unfavorable for the application to the spin-resolving device in the following two points.
Firstly, under no magnetic field, a ferromagnetic substance usually tends to split into many small domains with different directions of the electron spin polarization to energetically stabilize. In other words, the macroscopic spin polarization does not spontaneously occur despite the ferromagnetic nature. And, it is difficult in general to control and evaluate such a magnetic-domain structure.
Secondly, when a ferromagnetic spin polarization is attained over a macroscopic range somehow, the ferromagnetic substance itself generates a stray magnetic field. In the case that an external magnetic field is applied to achieve the macroscopic spin polarization, there also exists a stray magnetic field from an apparatus generating the external field. Such stray fields might affect the charge and/or the spin magnetic moment of a spin-polarized charged particle in the form of the Lorentz force, the magnetic force, and the Larmor precession.
One object of the invention is to provide a method of controlling properties of a ferromagnetic material, whereby it becomes suitably available for the spin-resolving technology for charged particles, which has no undesirable effect on the charge and/or the spin magnetic moment of the charged particle.
Another object of the invention is to provide a ferromagnetic material, where the properties suitable for the spin-resolving technology are easily materialized and controlled.
Further object of the invention is to provide a spin-resolving device for charged particles, which comprises a ferromagnetic material and, nonetheless, is free from the formation of magnetic domains and the leakage of a magnetic field.
DISCLOSURE OF THE INVENTION
A first feature of the invention is to control properties of a ferromagnetic substance, whose magnetization arises mainly from the element of samarium and in a method of this feature, the present ferromagnetic substance is so controlled as to keep a ferromagnetic alignment of the electron spin over a macroscopic range and to have a spin-orbital compensation property characterized by little or no magnetization due to the compensation between the two parts of the magnetization originating from the orbital magnetic moment and the spin one.
This spin-orbital compensation property can be attained at an arbitrary temperature by an appropriate modification of the composition of the ferromagnetic samarium substance and an appropriate preliminary thermomagnetic process.
The composition of the ferromagnetic samarium substance is controlled by, according to the relation in size between the partial magnetization originating from the orbital magnetic moment and that originating from the spin one, replacing a part of samarium in the base substance with other elements or adding other elements to the base substance so as to reduce the total magnetization.
A second feature of the invention lies in a ferromagnetic material, whose magnetization arises mainly from samarium and adapted to keep a ferromagnetic alignment of the electron spin therein over a macroscopic range and have a spin-orbital compensation property characterized by little or no magnetization due to the compensation between the two parts of the magnetization originating from the orbital magnetic moment and the spin one.
This ferromagnetic material is based on a ferromagnetic substance, whose magnetization arises mainly from samarium, and the composition of the ferromagnetic material is controlled by, according to the relation in size between the partial magnetization originating from the orbital magnetic moment and that originating from the spin one, replacing a part of samarium in the base substance with other elements or adding other elements to the base substance so as to reduce the total magnetization.
A third feature of the invention is to generate a spin-polarized charged-particle beam, measure the degree of the spin polarization or polarize or analyze the spin for a charged-particle flow (an electric current), making use of a spin-orbital compensation property of the ferromagnetic material, which serves as a spin-resolving device for charged particles.
As aforementioned, the ferromagnetic material of the invention comprises a substance, whose magnetization arises mainly from samarium, (referred to as “ferromagnetic samarium substance” hereafter) and the property suitable for the spin-resolving technology is the state, where the ferromagnetic samarium substance keeps the electron spin polarization aligning in one direction over a macroscopic range and has little or no magnetization.
This property of a ferromagnetic samarium substance can be basically attained by an appropriate modification of the composition and an appropriate preliminary thermomagnetic process. The reasons for that are described hereinafter.
Samarium usually has five 4f electrons in solids, but sometimes has six ones. In the following descriptions, only the former samarium is dealt with and is just called “samarium” hereafter.
For samarium, the spin magnetic moment due to the electrons' spin polarization and the orbital magnetic moment due to the electrons' orbital motion are almost the same in size, and couple in an opposite direction as a result of a relativistic effect, called the spin-orbit interaction, to form the total magnetic moment.
Therefore, a ferromagnetic samarium substance is intrinsically characterized by a quite small net magnetization owing to the marginal cancellation between the two parts of the magnetization originating from the spin magnetic moment and the orbital one.
Also, samarium is characterized by the difference in temperature dependence between the spin magnetic moment and the orbital one, which is ascribed to the narrow energy interval of about 1500 K (130 meV) between the ground J-multiplet (the lowest energy state) of the 4f e
Adachi Hiromichi
Ino Hiromitsu
Miwa Hirosi
Pearne & Gordon LLP
Sheehan John
LandOfFree
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