§ 2 Dia-and paramagnetic
Diamagnetic are those substances which have a magnetic moment of the atom in the absence of an external magnetic field is zero.
an external magnetic field is placed a substance, all the atoms of the
material are in a magnetic field that changes the motion of electrons
in the atom, so that an additional current, similar to the induction
current. If the vector and form an angle α, then in a magnetic field electron orbit will rotate around the direction with some angular velocity ( - Larmor precession frequency). Such movement mechanics called precession.
The precession of the
electron orbit is equivalent to an additional electron motion around
the magnetic field in addition to rotation around its axis of rotation
and orbit. This extra electron motion in the magnetic field leads to a
vicious induced current, which has a magnetic moment, which is always
directed against the field. Thus, the cause of the additional magnetic
moments - the precession of the orbit of the electron.
Since diamagnetics magnetized opposite to the magnetic field, their magnetization is negative.
For diamagnetic include metals Bi, Ag, Au, Cu; water, glass, inert gases, etc.
Diamagnetism is common to all substances, but a number of substances diamagnetic effect is blocked as stronger effects.
Paramagnetic called substances in which the atoms in the absence of an external magnetic field have some permanent magnetic moment
However, due to thermal motion of the magnetic moments are oriented randomly, so .
When a magnetic field,
forces that guide the magnetic moments of each atom. The magnetic
moments of trying to line up on the field. Thus, the paramagnetic
magnetized, creating its own magnetic field collinear with the
external field and reinforcing it.
The process of the magnetic moments of the atoms in a magnetic field is called the paramagnetic effect.
in paramagnetic forces are relatively small compared with the forces of
thermal motion, to break down the ordering. Therefore, with decreasing
temperature paramagnetic susceptibility usually increases.
Paramagnetic to include rare earth metals, Pt, Al, Mg, Cr, O2 etc.
§3 A magnetic field in the material.
Magnetic susceptibility and permeability
The current flowing through a conductor is called macrocurrent. The magnetic field generated by these currents, called the field of macrocurrent and denote macrocurrents. If an object is placed in this field , then the magnetic
moments of the atoms of matter will be oriented against the field in
the diamagnetic and paramagnetic in the field. Ie microcurrents
substances create an internal field ,opposite directions in the
diamagnetic and paramagnetic in collinear. Then the magnetic
induction vector of the resultant magnetic field in matter is equal to
the vector sum of the magnetic induction of the external field and microcurrents field
If we consider the
matter in any section of a cylinder perpendicular to its axis, the
substance inside the molecular currents of neighboring atoms are
directed towards each other and cancel each other out. Not be
compensated only molecular currents on the side of the cylinder. The
current through the cylinder surface is similar to the current in the
solenoid, and creates within it the field
; N = 1; µ = 1,
Experience shows that in weak magnetic fields, the magnetization is proportional to the field intensity , causing the magnetization
[χ] = 1
where χ - a dimensionless quantity called the magnetic susceptibility shows how the substance reacts (magnetized) to an external field .
-link permeability μ and susceptibility χ.
Magnetic permeability shows how many times the resulting magnetic field in a substance greater than the external magnetizing field macrocurrents .
χ < 0; µ < 1;
χ ~ 10-5 ÷ 10-7.
χ > 0; µ > 1;
χ ~ 10-3 ÷ 10-5.