Doped rareearth manganese oxides manganites exhibit a wide variety of physical phenomena due to comp

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(a)
(b)
Fig. 2. (a) Temperature dependence of the time
constant for the process shown in Fig. 1a after
sample illumination was switched off for sample
with gold nanoparticles on the surface (red) and
without (blue.) (b) Schematic illustration of
the appearance of photoinduced conductive phase
(green) (upper panel) and the increase of the
volume of this phase around gold nanoparticles.
Fig. 1. (a) Time dependence of the resistivity of
the Bi0.4Ca0.6MnO3 thin film at T 170 K after
illumination was switched on and off for sample
with gold nanoparticles on the surface (red
curve) and without (blue curve.) (b) AFM image of
gold nanoparticles on the surface of
Bi0.4Ca0.6MnO3 thin film
Doped rare-earth manganese oxides (manganites)
exhibit a wide variety of physical phenomena due
to complex interplay of electronic, magnetic,
orbital, and structural degrees of freedom and
their sensitivity to external fields. A
photoinduced insulator to conductor transition in
charge-ordered (CO) manganites is especially
interesting from the point of view of creating
photonic devices. We have found a considerable
increase (up to 50) of the photoinduced
resistivity changes (Fig. 1a) in the
Bi0.4Ca0.6MnO3 thin film after covering the
surface of the film with gold nanoparticles
(colloidal gold) (Fig. 1b). This increase can be
explained by enhancement of local electromagnetic
(EM) field in the vicinity of the gold
nanoparticle due to the plasmon resonance.
Moreover, the lifetime of the photoinduced
changes increases significantly after deposition
of the gold nanoparticles on the surface of the
film (Fig. 2a). From our previous studies we
have found that the magnitude and the lifetime of
photoinduced resistivity changes increases, when
intensity illumination increases, which is
probably due to the increase of the volume of
conducting phase, created by light. Therefore,
enhanced EM field in the vicinity of gold
particles promotes a formation of larger volume
of conducting phase (Fig. 2b).
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Education and Outreach Towson University is an
undergraduate institution with strong emphases on
undergraduate research. Three Towson students,
Robert Kennedy, Suguru Yokoyama, and Gene
Vanmeter, and one College of Notre Dame (local
college, which does not have a research program)
student Kim Wall were involved in this
research. Robert J. Kennedy has defended his
Departmental Honors Thesis based on his research.
After graduation Robert Kennedy had become a
high school science teacher, but continued his
research in summer as REU/RET (Research
Experience for Undergraduate/Teachers at Towson)
team participant with undergraduate student Mark
Steger from Albright College PA under the
mentorship of the PI.
To promote science among female students, the PI
have organized a half-day long field trip to
Towson University for 18 high school physics
students (all girls) of Mercy High School,
Towson, MD. The students showed active interest
during demonstrations, visited different
research, labs, received information about
careers in physics.
Undergraduate students K. Wall and M. Steger at
the REU/RET poster presentation.
Undergraduate students M. Steger and high school
science teacher R. Kennedy working in the lab.
High school physics students learning about
physics and materials research during their field
trip to Towson University.