SIUC Physics Seminar
School of Physics and Applied Physics, Southern Illinois University--Carbondale
2025 April 18 Friday 4:00 PM:
Physics Seminar in Neckers 440
Title: Analyzing the Magneto-optical Kerr effect using a rotating polarizer method
Speaker: Shusmita Podder Pooza
Team: Shusmita Podder Pooza, Hailey Potts, and Dipanjan Mazumdar
Affiliation: Southern Illinois University--Carbondale
Abstract:
The magneto-optical Kerr effect (MOKE) occurs when polarized light is reflected from a magnetized surface,
causing changes in polarization angle (called Kerr rotation) and its state (linear vs elliptical, for example).
In a simple version, MOKE measurement involves measuring the intensity of the reflected beam off the surface of
a sample as an external magnetic field is swept through it. We record a change in the reflected intensity when
the magnetization of the material changes. While easily measurable using modern electronics methods,
the Kerr rotation is minimal, only of the order of milliradians (∼0.1 deg), and is a characteristic
of the magnetic material. It is our goal to measure such small angles accurately.
Several parameters control the Kerr effect, including the incident polarization state, angle of incidence,
and the magnetic field. During the past year, I have developed a method to estimate the Kerr rotation accurately
using the incident beam polarization angle as a parameter. We have investigated the MOKE behavior using
a custom-built experimental setup equipped with a manually rotated polarizer, an optical chopper,
a lock-in amplifier, a beam splitter, and two detectors. I will present my data and analysis using the
Jones matrix formalism that allows us to obtain the Kerr rotation as a fitting parameter. Data will be
presented on standard magnetic systems such as Cobalt thin film and then applied to novel magnetic thin films
that interest our group. By recording the vertical and horizontal intensity of the reflected beam,
we show the Kerr effect is strong only for specific polarization states, and estimating the Kerr rotation
from a single measurement may lead to significant uncertainties, if not unmeasurable. Instead, the rotating
polarizer measurements developed here can provide a reliable measurement of Kerr rotation.
We will compare our results with existing literature.
Biography:
I am Shusmita Podder Pooza, a dedicated physics researcher and educator.
I completed my Bachelor of Science and Master of Science in Physics from the University of Dhaka,
one of the most prestigious institutions in Bangladesh. Currently,
I am pursuing my second master's degree in physics at Southern Illinois University, Carbondale,
where I joined in January 2024.
My research focuses on experimental condensed matter physics,
particularly the magneto-optical Kerr effect (MOKE). I study and quantify
the magnetic properties of novel magnetic thin films,
used to study the magnetization pattern in thin films.
This technique can characterize new materials used in memory storage devices.
Alongside my research, I work as a Graduate Teaching Assistant,
conducting lab sessions and assisting students in hands-on experimental learning.
My passion for physics extends beyond the classroom,
and I genuinely enjoy exploring new experiments and engaging with students
during my TA responsibilities.
Outside of academics, I have a deep fascination with the sky--I love observing its color changes,
spotting planets with the naked eye, and witnessing breathtaking sunrises and sunsets.
I also have a strong passion for tracking weather patterns and exploring nature's wonders.
My fascination with the beauty and dynamics of the sky is an endless source of inspiration for me.
Last updated on
by K V Shajesh
(kvshajesh@gmail.com).