Define “Magneto-striction”? State the causes for loss of magnetism.
2 Answers
**Magnetostriction** is the phenomenon where a material changes its shape or dimensions when subjected to a magnetic field. This effect occurs due to the interaction between the magnetic field and the magnetic dipole moments within the material, which leads to a change in the internal magnetic structure and consequently the physical dimensions of the material.
**Causes for Loss of Magnetism:**
1. **Temperature Effects:** Increasing temperature can cause the loss of magnetism in materials. In ferromagnetic materials, this is known as the Curie temperature. Above this temperature, the material loses its magnetic properties and becomes paramagnetic.
2. **Magnetic Saturation:** When a material reaches its magnetic saturation point, it can no longer increase its magnetization despite the increase in the external magnetic field, leading to a loss of practical magnetism for certain applications.
3. **Hysteresis Loss:** During magnetic field reversal, some energy is lost due to internal friction and lag, which can lead to a gradual loss of magnetism over time.
4. **Aging:** Materials can lose magnetism due to aging effects. Over time, the alignment of magnetic domains may become less effective, reducing the material's magnetic properties.
5. **Mechanical Stress:** Applying mechanical stress to a magnetic material can disrupt its magnetic domains, leading to a decrease in magnetism.
6. **Chemical Corrosion:** Chemical reactions or corrosion can alter the magnetic properties of materials by changing their composition or structure.
7. **Exposure to External Magnetic Fields:** Strong external magnetic fields can realign the magnetic domains in a way that causes a loss of the original magnetic orientation.
Understanding these causes helps in designing materials and devices that maintain their magnetic properties under various conditions.
**Causes for Loss of Magnetism:**
1. **Temperature Effects:** Increasing temperature can cause the loss of magnetism in materials. In ferromagnetic materials, this is known as the Curie temperature. Above this temperature, the material loses its magnetic properties and becomes paramagnetic.
2. **Magnetic Saturation:** When a material reaches its magnetic saturation point, it can no longer increase its magnetization despite the increase in the external magnetic field, leading to a loss of practical magnetism for certain applications.
3. **Hysteresis Loss:** During magnetic field reversal, some energy is lost due to internal friction and lag, which can lead to a gradual loss of magnetism over time.
4. **Aging:** Materials can lose magnetism due to aging effects. Over time, the alignment of magnetic domains may become less effective, reducing the material's magnetic properties.
5. **Mechanical Stress:** Applying mechanical stress to a magnetic material can disrupt its magnetic domains, leading to a decrease in magnetism.
6. **Chemical Corrosion:** Chemical reactions or corrosion can alter the magnetic properties of materials by changing their composition or structure.
7. **Exposure to External Magnetic Fields:** Strong external magnetic fields can realign the magnetic domains in a way that causes a loss of the original magnetic orientation.
Understanding these causes helps in designing materials and devices that maintain their magnetic properties under various conditions.
### Magnetostriction
**Magnetostriction** is the phenomenon by which a magnetic material changes its shape or dimensions when subjected to a magnetic field. This effect is observed in ferromagnetic materials, where the material undergoes mechanical deformation due to changes in the magnetic alignment of its domains.
#### **How Magnetostriction Works**
- **Magnetic Domains**: In a ferromagnetic material, magnetic domains are regions where the magnetic moments of atoms are aligned in the same direction. When a magnetic field is applied, these domains can change in size and orientation to align with the external field.
- **Shape Change**: As the domains align with the magnetic field, the material can expand or contract. This change in dimensions is known as magnetostriction. The amount of deformation is typically very small but measurable.
#### **Applications of Magnetostriction**
- **Actuators**: Magnetostrictive materials are used in actuators to convert magnetic energy into mechanical movement.
- **Sensors**: They are used in sensors to measure magnetic fields and mechanical stress.
### Causes of Loss of Magnetism
Magnetism in materials can diminish or be lost due to several factors:
1. **Temperature**:
- **Curie Temperature**: For ferromagnetic materials, there is a critical temperature called the Curie temperature above which the material loses its ferromagnetic properties and becomes paramagnetic. This is because the thermal energy disrupts the alignment of magnetic domains.
- **Thermal Fluctuations**: Even below the Curie temperature, high temperatures can cause increased thermal vibrations, disrupting the alignment of domains and reducing magnetization.
2. **Mechanical Stress**:
- **Strain**: Mechanical stress can alter the shape of the material, leading to changes in the domain structure and reducing the material's magnetization.
- **Magnetostriction**: Excessive magnetostriction can also lead to a loss of magnetism if the material’s structure changes significantly.
3. **Exposure to High Magnetic Fields**:
- **Saturation**: Prolonged exposure to very high magnetic fields can saturate the material, pushing the magnetic domains to their maximum alignment and potentially leading to a reduction in the material’s ability to respond to additional magnetic fields.
4. **Magnetic Field Reversal**:
- **Demagnetization**: Repeated exposure to alternating or reverse magnetic fields can lead to a loss of magnetization by disrupting the alignment of magnetic domains.
5. **Aging**:
- **Material Degradation**: Over time, the material can undergo changes due to environmental factors like oxidation or chemical reactions, which can affect its magnetic properties.
6. **Electrical Currents**:
- **Eddy Currents**: In some cases, electrical currents induced in the material by changing magnetic fields can lead to localized heating or other effects that reduce magnetization.
Understanding these causes is crucial in applications requiring stable magnetic properties, such as in permanent magnets, magnetic sensors, and transformers.
**Magnetostriction** is the phenomenon by which a magnetic material changes its shape or dimensions when subjected to a magnetic field. This effect is observed in ferromagnetic materials, where the material undergoes mechanical deformation due to changes in the magnetic alignment of its domains.
#### **How Magnetostriction Works**
- **Magnetic Domains**: In a ferromagnetic material, magnetic domains are regions where the magnetic moments of atoms are aligned in the same direction. When a magnetic field is applied, these domains can change in size and orientation to align with the external field.
- **Shape Change**: As the domains align with the magnetic field, the material can expand or contract. This change in dimensions is known as magnetostriction. The amount of deformation is typically very small but measurable.
#### **Applications of Magnetostriction**
- **Actuators**: Magnetostrictive materials are used in actuators to convert magnetic energy into mechanical movement.
- **Sensors**: They are used in sensors to measure magnetic fields and mechanical stress.
### Causes of Loss of Magnetism
Magnetism in materials can diminish or be lost due to several factors:
1. **Temperature**:
- **Curie Temperature**: For ferromagnetic materials, there is a critical temperature called the Curie temperature above which the material loses its ferromagnetic properties and becomes paramagnetic. This is because the thermal energy disrupts the alignment of magnetic domains.
- **Thermal Fluctuations**: Even below the Curie temperature, high temperatures can cause increased thermal vibrations, disrupting the alignment of domains and reducing magnetization.
2. **Mechanical Stress**:
- **Strain**: Mechanical stress can alter the shape of the material, leading to changes in the domain structure and reducing the material's magnetization.
- **Magnetostriction**: Excessive magnetostriction can also lead to a loss of magnetism if the material’s structure changes significantly.
3. **Exposure to High Magnetic Fields**:
- **Saturation**: Prolonged exposure to very high magnetic fields can saturate the material, pushing the magnetic domains to their maximum alignment and potentially leading to a reduction in the material’s ability to respond to additional magnetic fields.
4. **Magnetic Field Reversal**:
- **Demagnetization**: Repeated exposure to alternating or reverse magnetic fields can lead to a loss of magnetization by disrupting the alignment of magnetic domains.
5. **Aging**:
- **Material Degradation**: Over time, the material can undergo changes due to environmental factors like oxidation or chemical reactions, which can affect its magnetic properties.
6. **Electrical Currents**:
- **Eddy Currents**: In some cases, electrical currents induced in the material by changing magnetic fields can lead to localized heating or other effects that reduce magnetization.
Understanding these causes is crucial in applications requiring stable magnetic properties, such as in permanent magnets, magnetic sensors, and transformers.