Diamagnetic Materials
- Substances that are repelled by a magnetic field
- Atomic electrons in these materials re-arrange their orbits opposite to the direction of an applied field
- Examples: bismuth, water, gold, zinc
Properties of Diamagnetic Materials
- Weakly magnetized in an external magnetic field
- No permanent magnetic moments
- Magnetic susceptibility is negative and close to zero
- Magnetic field lines tend to move away from diamagnetic substances
Paramagnetic Materials
- Substances that are weakly attracted to a magnetic field
- Atomic electrons in these materials align their magnetic moments with an applied field, but the alignment is temporary
- Examples: aluminum, platinum, oxygen, copper
Properties of Paramagnetic Materials
- Weakly magnetized in an external magnetic field
- Possess some permanent magnetic moments
- Magnetic susceptibility is positive and small
- Magnetic field lines tend to move towards paramagnetic substances
Ferromagnetic Materials
- Substances that are strongly attracted to a magnetic field
- Atomic electrons in these materials align their magnetic moments with an applied field and retain the alignment even after the external field is removed
- Examples: iron, nickel, cobalt
Properties of Ferromagnetic Materials
- Strongly magnetized in an external magnetic field
- Possess permanent magnetic moments
- Magnetic susceptibility is positive and large
- Magnetic field lines tend to concentrate within ferromagnetic substances due to their high permeability
Magnetic Field of the Earth
- Earth has its own magnetic field which is generated due to the movement of molten iron and nickel in its outer core
- Acts like a giant bar magnet with its magnetic south pole located near the geographic north pole and its magnetic north pole located near the geographic south pole
Magnetic Field Lines of the Earth
- Magnetic field lines always point from the north magnetic pole to the south magnetic pole
- Magnetic field lines are not perfectly aligned with the geographic axis, causing a declination (angle between true north and magnetic north) at any given location
- Magnetic field lines are inclined to the surface of the Earth, causing a dip or inclination at any given location
Hysteresis
- Hysteresis is a phenomenon observed in magnetic materials, particularly ferromagnetic substances
- It refers to the lagging of the magnetization of a material behind the strength of the magnetic field applied to it
- Hysteresis is caused by the internal magnetic domains in the material taking time to align with the external field
Magnetic Hysteresis Loop
- The relationship between the magnetizing field and the magnetization of a material can be represented by a magnetic hysteresis loop
- The loop shows how the magnetization of the material changes as the external magnetic field is increased and then decreased
- The width of the loop represents the coercive force of the material, which is the amount of magnetic field required to completely demagnetize it
Diamagnetic, Paramagnetic, and Ferromagnetic Materials
- Diamagnetic, paramagnetic, and ferromagnetic materials are classified based on their behavior in the presence of a magnetic field.
- Diamagnetic materials are repelled by a magnetic field, while paramagnetic materials are weakly attracted to it and ferromagnetic materials are strongly attracted to it.
- These behaviors arise from the response of atomic electrons to the applied magnetic field.
Diamagnetic Materials
- Diamagnetic materials have all electrons paired, resulting in zero net magnetic moment.
- When exposed to a magnetic field, the orbital motion of the electrons creates an opposing magnetic field, causing the material to be repelled.
- Diamagnetic materials exhibit weak magnetization and do not retain magnetic properties after removing the applied field.
- Examples of diamagnetic materials include bismuth, water, gold, and zinc.
Paramagnetic Materials
- Paramagnetic materials have unpaired electrons, resulting in a net magnetic moment.
- In the absence of a magnetic field, the magnetic moments of the electrons are randomly oriented.
- When a magnetic field is applied, the moments tend to align with the field, causing the material to be weakly attracted.
- Paramagnetic materials exhibit small positive magnetic susceptibility and weak magnetization.
- Examples of paramagnetic materials include aluminum, platinum, oxygen, and copper.
Ferromagnetic Materials
- Ferromagnetic materials have spontaneous magnetization due to the alignment of atomic magnetic moments.
- Each atom in a ferromagnet acts as a tiny magnet, and the alignment of these moments leads to a strong net magnetization.
- Ferromagnetic materials can retain their magnetization even after removing the applied field.
- Examples of ferromagnetic materials include iron, nickel, and cobalt.
Magnetic Field of the Earth
- The Earth itself generates a magnetic field, which is like that of a giant bar magnet.
- The outer core of the Earth, comprising molten iron and nickel, gives rise to this magnetic field.
- The Earth’s magnetic field has its magnetic south pole near the geographic north pole and its magnetic north pole near the geographic south pole.
Magnetic Field Lines of the Earth
- Magnetic field lines of the Earth follow certain patterns.
- Field lines always point from the magnetic north pole to the magnetic south pole.
- Field lines are not parallel to the geographic axis, causing a declination angle between true north and magnetic north at a location.
- Field lines are inclined to the surface of the Earth, causing a dip or inclination angle at a location.
Hysteresis
- Hysteresis is observed in magnetic materials, especially ferromagnetic substances.
- It refers to the lagging of magnetization behind the applied magnetic field strength.
- This behavior arises due to internal magnetic domains taking time to align with the external field.
- Hysteresis can be observed by plotting the magnetization as a function of the applied magnetic field strength.
Magnetic Hysteresis Loop
- A magnetic hysteresis loop represents the relationship between the magnetizing field and the magnetization of a material.
- The loop shows the changes in magnetization as the external field is increased and then decreased.
- The hysteresis loop’s width represents the coercive force, which is the field required to demagnetize the material completely.
- The loop’s shape provides valuable information about the material’s magnetic properties and behavior.
Magnetic Hysteresis Loop Example
- For ferromagnetic materials, the magnetic hysteresis loop exhibits a characteristic shape.
- Initially, as the magnetic field increases, the magnetization of the material also increases in a nonlinear manner.
- When the field reaches a saturation point, further increase does not significantly affect the magnetization.
- On decreasing the field, the material retains some magnetization until reaching the coercive force, where it becomes demagnetized.
Applications of Magnetic Hysteresis
- Magnetic hysteresis finds applications in various devices and technologies:
- Magnetic storage devices like hard disks rely on the magnetic hysteresis of ferromagnetic materials to store and retrieve data.
- Electric motors and transformers utilize hysteresis to efficiently convert electrical energy into mechanical energy.
- Magnetic shielding materials use hysteresis to redirect and dissipate stray magnetic fields, protecting sensitive electronic components.
Diamagnetic, Paramagnetic, and Ferromagnetic Materials
- Diamagnetic, paramagnetic, and ferromagnetic materials are classified based on their behavior in the presence of a magnetic field.
Diamagnetic Materials
- Diamagnetic materials have all electrons paired, resulting in zero net magnetic moment.
- When exposed to a magnetic field, the orbital motion of the electrons creates an opposing magnetic field, causing the material to be repelled.
- Diamagnetic materials exhibit weak magnetization and do not retain magnetic properties after removing the applied field.
- Examples of diamagnetic materials: bismuth, water, gold, zinc.
Paramagnetic Materials
- Paramagnetic materials have unpaired electrons, resulting in a net magnetic moment.
- In the absence of a magnetic field, the magnetic moments of the electrons are randomly oriented.
- When a magnetic field is applied, the moments tend to align with the field, causing the material to be weakly attracted.
- Paramagnetic materials exhibit small positive magnetic susceptibility and weak magnetization.
- Examples of paramagnetic materials: aluminum, platinum, oxygen, copper.
Ferromagnetic Materials
- Ferromagnetic materials have spontaneous magnetization due to the alignment of atomic magnetic moments.
- Each atom in a ferromagnet acts as a tiny magnet, and the alignment of these moments leads to a strong net magnetization.
- Ferromagnetic materials can retain their magnetization even after removing the applied field.
- Examples of ferromagnetic materials: iron, nickel, cobalt.
Magnetic Field of the Earth
- The Earth itself generates a magnetic field due to the movement of molten iron and nickel in its outer core.
Magnetic Field Lines of the Earth
- Magnetic field lines of the Earth follow certain patterns.
- Field lines always point from the magnetic north pole to the magnetic south pole.
- Field lines are not parallel to the geographic axis, causing a declination angle between true north and magnetic north at a location.
- Field lines are inclined to the surface of the Earth, causing a dip or inclination angle at a location.
Hysteresis
- Hysteresis is observed in magnetic materials, especially ferromagnetic substances.
- It refers to the lagging of magnetization behind the applied magnetic field strength.
Magnetic Hysteresis Loop
- A magnetic hysteresis loop represents the relationship between the magnetizing field and the magnetization of a material.
- The loop shows the changes in magnetization as the external field is increased and then decreased.
- The hysteresis loop’s width represents the coercive force, which is the field required to demagnetize the material completely.
- The loop’s shape provides information about the material’s magnetic properties and behavior.
Application of Hysteresis
- Magnetic hysteresis finds applications in various devices and technologies:
- Magnetic storage devices like hard disks rely on the magnetic hysteresis of ferromagnetic materials to store and retrieve data.
- Electric motors and transformers utilize hysteresis to efficiently convert electrical energy into mechanical energy.
- Magnetic shielding materials use hysteresis to redirect and dissipate stray magnetic fields, protecting sensitive electronic components.
Summary
- Diamagnetic materials are repelled by a magnetic field, while paramagnetic and ferromagnetic materials are weakly attracted to it.
- Diamagnetic materials have all electrons paired, paramagnetic materials have unpaired electrons, and ferromagnetic materials have aligned atomic magnetic moments.
- The Earth has a magnetic field generated by the movement of molten iron and nickel in its outer core.
- Magnetic hysteresis refers to the lagging of magnetization behind the applied magnetic field strength and is displayed in ferromagnetic materials.
- The hysteresis loop provides information about the material’s magnetic properties and finds various applications in technology.
Diamagnetic Materials Substances that are repelled by a magnetic field Atomic electrons in these materials re-arrange their orbits opposite to the direction of an applied field Examples: bismuth, water, gold, zinc