Influence of heat treatment on the structural and magnetic characteristics of (NdxPr1-x)2Fe14B-based magnetic material for low-temperature application

Sintered Pr-Nd-Fe-B-based permanent magnets with 10 and 13 wt. % of Pr were prepared by traditional technology and then subjected to various heat treatments. Stoichiometric composition of the matrix grains corresponds to (Pr0.3Nd0.7)2Fe14B and (Pr0.4Nd0.6)2Fe14B compounds, respectively. Conducted thermomagnetic analysis to samples of these magnets showed the presence of spin-reorientation transition in temperature 95 and 75 K, respectively. This makes the magnet potentially applicable for low temperatures. For these compounds, we have determined the optimum heat-treatment conditions. The magnetic domain structure of the magnet subjected to an optimum heat treatment has been studied. The effect of different low-temperature heat treatments on the magnetic properties of magnets has been demonstrated

Surface magnetic properties and domains observation in as-quenched and annealed FeNbB ribbons

The longitudinal magneto-optical Kerr effect (MOKE) combined with the magneto-optical microscopy is used to investigate the surface magnetic anisotropy and the domain behavior in as-quenched (AQ) and strain-annealed (SA) FeNbB ribbons. X-ray diffraction, conversion electron Mössbauer spectroscopy (CEMS), and scanning electron microscopy (SEM) confirmed the existence of approximately View the MathML source thick magnetically harder layer on the ribbon air side, consisting of crystallites embedded in an amorphous matrix. The underneath bulk phase is amorphous and magnetically soft. Residual anisotropies and the domain patterns (wide in-plane domains with 180ring operator walls and narrow fingerprint domains) corresponding to amorphous phase are mainly caused by the internal stresses originating from the rapid quenching process. In the surface crystalline phase they are gradually overlapped by strip domains with magnetization directions almost perpendicular to the ribbon axis. The anisotropy changes caused by additional annealing and straining of the samples are shown and discussed in detail

Depth-sensitive characterization of surface magnetic properties of as-quenched FeNbB ribbons

The longitudinal magneto-optical Kerr effect (MOKE) is used to study the surface magnetic properties of as-quenched FeNbB ribbons. MOKE surface hysteresis loops measured from both ribbon sides confirm different magnetic behavior. Wheel ribbon side shows heterogeneous (crystalline/amorphous) properties, thickness of crystalline phase (about 3 nm) was established by comparing the measured magneto-optical angles of Kerr rotation and ellipticity at different incident angles with the theoretical model. Effective crystalline phase observed at shiny ribbon side is harder (coercive field about 40 Oe) than that on wheel side and penetrates deeper into the material volume. Its thickness 1.3 m estimated from the weight reduction of the ribbon during surface etching is in good agreement with cross-section image obtained using the scanning electron microscopy (SEM). The sources of magnetoelastic anisotropy were identified in the bulk as well as on the ribbon surface using the magneto-optical Kerr microscopy

Influence of heat treatment on the structural and magnetic characteristics of (Nd_xPr_1-x)₂Fe₁₄B-based magnetic material for low-temperature application

Sintered Pr-Nd-Fe-B-based permanent magnets with 10 and 13 wt. % of Pr were prepared by traditional technology and then subjected to various heat treatments. Stoichiometric composition of the matrix grains corresponds to (Pr_0.3Nd_0.7)₂Fe₁₄B and (Pr_0.4Nd_0.6)₂Fe₁₄B compounds, respectively. Conducted thermomagnetic analysis to samples of these magnets showed the presence of spin-reorientation transition in temperature 95 and 75 K, respectively. This makes the magnet potentially applicable for low temperatures. For these compounds, we have determined the optimum heat-treatment conditions. The magnetic domain structure of the magnet subjected to an optimum heat treatment has been studied. The effect of different low-temperature heat treatments on the magnetic properties of magnets has been demonstrated

Ramp it up and down

We describe a simple experiment about sliding friction of an object moving with non-constant speed along an inclined plane. This experiment can be used to study the entire dynamical process of force and motion in various ways, depending on the mathematical level of the students. We discuss how video measurement and analysis, and mathematical modelling with adequate computer tools let upper secondary students focus on physics concepts, move back and forth between theory and practice, and make connections between all involved quantities, without being distracted by cumbersome measurements and calculations. We also present some advanced models for friction phenomena that become within reach of students via computational modelling