Colossal Magnetocapacitance in Mixed Phase (La0.33Pr0.33Ca0.34MnO3 ) Manganites

Arthur F. Hebard, University of Florida, DMR-0404962

Colossal magnetocapacitance (CMC) has been observed in planar capacitor structures comprising a manganite film separated from an aluminum counter electrode by a thin oxide layer. The effect is termed ‘colossal’ because of the factor of 1000 change in capacitance induced by application of a magnetic field. The underlying physics giving rise to this unusually large effect is the temperature and field-dependent competition between ferro-magnetic metallic and paramagnetic insulating phases in the manganite electrode. Because capacitance is sensitive to surfaces and inter-faces, critical information about surface magnetism including relaxation times, phase boundaries and hysteresis can be extracted from these measurements.

Figure 1: Temperature dependent capacitance of a La0.33Pr0.33Ca0.34MnO3 (LPCMO) capacitor structure at the indicated magnetic fields. The inset is a magnification of the zero field data superimposed upon the simultaneously measured loss peaks. The temperature and field dependent positions of these peaks determine boundaries for competing surface magnetic phases.

0 100 200 300

100

101

102

103

40 50 60 70 80 90

100

101

102

103

0.0

0.4

0.8

1.2

H to plane

0 kOe 10 kOe 20 kOe 50 kOe

C (p

F)Temperature

C

C (p

F)

H=0 Oe Loss

Los

s (

S)T T

Colossal Magnetocapacitance in Mixed Phase (La0.33Pr0.33Ca0.34MnO3 ) Manganites

Arthur F. Hebard, University of Florida, DMR-0404962

High school student Paula Te enjoying a relaxing moment with first year graduate student Rajiv Singh in front of their experiment to measure the frequency dependent capacitance of ferrofluids.

Societal Impact, Education and Outreach:The central theme of this grant addresses the use of capacitance measurements to study magnetic pro-perties of electronic interfaces. Such studies are important to understand surface magnetism as well as to assess the potential of novel materials in pro-mising new magnetoelectronic technologies. A recent PhD graduate, who was supported by this grant, pioneered the use of magneto-capacitance measurements [1] and is presently employed as a member of the research staff at Intel. Two additional PhD students will soon graduate. Resources of the grant are also used to provide research experiences to undergraduates, REU and high school students.

[1] “Magnetocapacitance: A probe of spin-dependent potentials”, K. T. McCarthy et al., Phys. Rev. Lett. 90, 117201 (2003).