Lecture 13: Magnetic Properties Flashcards
Describe what a Bohr Magneton represents
A Bohr Magneton is a physical constant that quantifies the magnetic moment typical of an electron due to its orbital or spin angular momentum.
What is ferromagnetism?
Ferromagnetism is a type of magnetism where magnetic moments of atoms align parallel to each other within a material, creating strong internal magnetization.
Explain the concept of antiferromagnetism.
Antiferromagnetism is a type of magnetism in which adjacent ions align themselves with opposite spins, resulting in no net magnetic moment at a macroscopic scale.
What is ferrimagnetism?
Ferrimagnetism occurs when magnetic moments of adjacent atoms align in opposite directions, but in unequal strengths, causing a net magnetic moment.
Define helimagnetism.
Helimagnetism is a type of magnetic ordering where spins on adjacent atoms twist around the axis moving through the crystal instead of aligning straight.
What is a spin glass state?
A spin glass state is a magnetic state characterized by disordered magnetic moments that are frozen into place upon cooling, without long-range magnetic order.
How does Lenz’s Law relate to diamagnetism?
Lenz’s Law in diamagnetism describes how induced magnetic fields in a material oppose the change in the external magnetic field that induced them.
What is magnetic flux density?
Magnetic flux density, represented as B, is the measure of the magnetic field’s strength within a medium.
What does magnetization (M) indicate about a material?
Magnetization indicates the degree to which a material becomes magnetized when placed in an external magnetic field and is defined as the net magnetic moment per unit volume.
Define magnetic susceptibility.
Magnetic susceptibility is a dimensionless proportionality constant that indicates how much a material will become magnetized in an external magnetic field.
What is the Curie Law?
The Curie Law states that the magnetic susceptibility of a paramagnetic material is inversely proportional to its temperature.
Describe the Curie-Weiss Law.
The Curie-Weiss Law modifies the Curie Law by incorporating a temperature offset known as the Weiss constant, reflecting interactions between spins.
What is the significance of the Neel temperature?
The Neel temperature is the temperature below which an antiferromagnetic material transitions to a paramagnetic state.
Explain what is meant by Pauli paramagnetism.
Pauli paramagnetism is a type of magnetism exhibited by conduction electrons in metals that are influenced by Pauli’s exclusion principle.
How does the 4d band relate to ferromagnetism in transition metals?
In transition metals, the density of states at the Fermi level within the 4d band must be high for ferromagnetism to occur, as this enhances the exchange interactions leading to parallel spin alignment.
What is ferromagnetic exchange coupling?
Ferromagnetic exchange coupling is the interaction that causes atomic magnetic moments in ferromagnetic material to align parallel to each other.
Describe ferromagnetic domains.
Ferromagnetic domains are regions within a ferromagnetic material where the magnetic moments are uniformly aligned; the direction of alignment varies from one domain to another.
What is magnetic hysteresis?
Magnetic hysteresis is the lagging of magnetization behind the magnetizing force, typically illustrated with a hysteresis loop graph showing the relationship between applied magnetic field and magnetization.
Define coercive force.
Coercive force is the intensity of the applied magnetic field required to reduce the magnetization of a ferromagnetic material to zero after achieving saturation.
What is the difference between soft and hard magnetic materials?
Soft magnetic materials have low coercivity and are easy to magnetize and demagnetize, while hard magnetic materials have high coercivity and retain their magnetism.
What are rare earth magnets and why are they important?
Rare earth magnets are strong permanent magnets made from alloys of rare earth elements. They are important due to their ability to provide significant magnetic strength in compact sizes, crucial for various modern technologies.
Explain the role of giant magnetoresistance (GMR) in technology.
Giant magnetoresistance is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and non-magnetic layers. GMR is crucial for developing sensitive read heads in modern hard disk drives.
What is a magnetic dipole?
A magnetic dipole consists of two magnetic poles, north and south, separated by a distance but linked by magnetic lines of force.
Define magnetic moment.
Magnetic moment is a vector quantity that represents the magnetic strength and orientation of a magnet or other object that produces a magnetic field.
