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Room-Temperature Low-Field Colossal Magnetoresistance in Double-Perovskite Manganite
S Yamada1, N Abe2, H Sagayama3,4
1Department of Materials System Science, Yokohama City University, Yokohama 236-0027, Japan.
Physical Review Letters
|October 22, 2019
Summary
Researchers discovered room-temperature colossal magnetoresistance (CMR) in NdBaMn₂O₆ crystals. This effect shows a significant resistance change at low magnetic fields near 300 K, driven by melting charge and orbital ordering.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Magnetism and Spintronics
Background:
- Colossal Magnetoresistance (CMR) is a significant phenomenon in certain materials, typically observed at low temperatures and high magnetic fields.
- Understanding the mechanisms behind CMR is crucial for developing advanced magnetic sensors and memory devices.
- A-site ordered perovskites containing manganese oxides are known for exhibiting complex magnetic and electronic phase transitions.
Purpose of the Study:
- To investigate the occurrence of colossal magnetoresistance (CMR) in NdBaMn₂O₆ crystals.
- To characterize the conditions (temperature and magnetic field) under which CMR appears.
- To elucidate the underlying physical mechanisms responsible for the observed CMR effect.
Main Methods:
- Synthesis and characterization of A-site ordered NdBaMn₂O₆ crystals.
- Electrical resistance measurements as a function of temperature and magnetic field.
- Analysis of the magnetic-field-temperature (B-T) phase diagram to estimate entropy changes.
Main Results:
- Discovery of room-temperature, low-field CMR in NdBaMn₂O₆, with resistance changing over two orders of magnitude below 2 T near 300 K.
- Sharp transitions between insulating and metallic phases occurring within 1 K and 0.5 T.
- Observed entropy change is smaller than expected for charge and orbital ordering, attributed to suppressed short-range ferromagnetic fluctuations of Mn spin moments.
Conclusions:
- The CMR effect in NdBaMn₂O₆ is attributed to the melting of charge and orbital ordering.
- The suppression of entropy change, linked to the loss of short-range ferromagnetic fluctuations, is key to achieving high-temperature, low-field CMR.
- This finding opens avenues for novel applications utilizing CMR at ambient conditions.
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