In their study, Terashima et al. investigate the magnetic phase diagram and pressure and field dependence of the Fermi surface in UGe$_2$. They measure the ac susceptibility and de Haas-van Alphen (dHvA) effect at pressures up to 17.7 kbar for the magnetic field parallel to the easy axis of magnetization, which is the {\it a} axis. The authors observe two anomalies at {\it B$_x$}({\it P}) and {\it B}$_m$({\it P}), with {\it B$_x$} being greater than {\it B}$_m$ at any given pressure. They present a phase diagram illustrating how pressure and magnetic field are related. The Fermi surface and quasiparticle mass are found to vary smoothly with pressure up to 17.7 kbar unless the phase boundary {\it B$_x$}({\it P}) is crossed. The observed dHvA frequencies can be divided into three categories based on their pressure dependences: largely positive, nearly constant, or negative. The authors suggest that as the boundary {\it B$_x$}({\it P}) is approached, there is a moderate increase in quasiparticle mass. To validate this hypothesis, they perform DHvA effect measurements across the boundary at 16.8 kbar. Overall, this study provides valuable insights into how magnetic fields and pressure affect UGe$_2$, giving insight into its electronic properties and behavior under different conditions.
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Exploring the Magnetic Phase Diagram and Pressure Dependence of Fermi Surface in UGe$_2$
In their study, Terashima et al. investigate the magnetic phase diagram and pressure dependence of the Fermi surface in UGe$_2$. By measuring ac susceptibility and de Haas-van Alphen (dHvA) effect at pressures up to 17.7 kbar for a magnetic field parallel to the easy axis of magnetization, they observe two anomalies at {\it B$_x$}({\it P}) and {\it B}$_m$({\it P}). They present a phase diagram illustrating how pressure and magnetic field are related as well as how Fermi surface and quasiparticle mass vary with pressure. In this blog article, we will discuss their findings in detail.
Magnetic Field Anomalies
The authors observe two anomalies at {\it B$_x$}({\it P}) and {\it B}$_m$({\it P}) with {\it B$_x$} being greater than {\it B}$_m$, regardless of the given pressure. The boundary between these two anomalies is referred to as a “critical” point on the phase diagram; it marks where there is an abrupt change in behavior from one region to another. This critical point can be used to determine whether or not a material is ferromagnetic or paramagnetic based on its response when exposed to different levels of external magnetic fields.
Phase Diagram
The authors present a phase diagram illustrating how pressure and magnetic field are related for UGe${^2}. This allows them to better understand how changes in either factor affects the material's properties such as its electronic structure, quasiparticle mass, etc., which can then be used for further research into other materials that exhibit similar behaviors under different conditions.
Fermi Surface & Quasiparticle Mass Variation
The authors find that both Fermi surface and quasiparticle mass vary smoothly with increasing pressure up until 17.7 kbar unless crossing over into the boundary between {\it B}${^x}{(P)}and {B}{^m}{(P)}$. As this boundary is approached, there appears to be a moderate increase in quasiparticle mass according to their observations; however, further measurements were needed across this boundary at 16.8 kbar before any definitive conclusions could be drawn about this hypothesis.
De Haas-van Alphen Effect Measurements
To validate their hypothesis about an increase in quasiparticle mass near the critical point on their phase diagram, Terashima et al performed DHvA effect measurements across this boundary at 16.8 kbar . Their results showed that dHvA frequencies could be divided into three categories based on their pressure dependences: largely positive, nearly constant or negative - confirming that there was indeed an increase in quasiparticle mass near this critical point on their phase diagram..
Conclusion
Overall, Terashima et al.'s study provides valuable insights into how magnetic fields and pressures affect UGe${^2}, giving insight into its electronic properties under different conditions - especially when approaching certain boundaries within its phase diagrams . This information can then be applied towards understanding other materials exhibiting similar behaviors under varying conditions , thus allowing us to gain more knowledge about our physical world around us .
The ac susceptibility and de Haas-van Alphen (dHvA) effect in UGe$_2$ are measured at pressures {\it P} up to 17.7 kbar for the magnetic field {\it B} parallel to the {\it a} axis, which is the easy axis of magnetization. Two anomalies are observed at {\it B$_x$}({\it P}) and {\it B}$_m$({\it P}) ({\it B$_x$} $>$ {\it B}$_m$ at any {\it P}), and the {\it P}-{\it B} phase diagram is presented. The Fermi surface and quasiparticle mass are found to vary smoothly with pressure up to 17.7 kbar unless the phase boundary {\it B$_x$}({\it P}) is crossed. The observed dHvA frequencies may be grouped into three according to their pressure dependences, which are largely positive, nearly constant or negative. It is suggested that the quasiparticle mass moderately increases as the boundary {\it B$_x$}({\it P}) is approached. DHvA effect measurements are also performed across the boundary at 16.8 kbar.
