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Spin-glass behavior in LaFe(x)Co(2-x)P2 solid solutions: interplay between magnetic properties and crystal and
Kirill Kovnir1, V Ovidiu Garlea, Corey M Thompson
1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA.
Inorganic Chemistry
|September 17, 2011
Summary
This study investigates how substituting iron for cobalt in LaFe(x)Co(2-x)P(2) compounds affects magnetic properties, revealing a transition from ferromagnetic to paramagnetic behavior with increasing iron content.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Magnetism
Background:
- The ThCr(2)Si(2) structure type hosts compounds with interesting magnetic properties.
- Understanding the evolution of magnetism with chemical composition is crucial for materials design.
- Lanthanum cobalt phosphides (LaCo(2)P(2)) are ferromagnetic, while lanthanum iron phosphides (LaFe(2)P(2)) are paramagnetic.
Purpose of the Study:
- To investigate the magnetic property evolution in LaFe(x)Co(2-x)P(2) solid solutions.
- To determine the critical iron concentration for suppressing ferromagnetic ordering.
- To elucidate the underlying electronic and structural factors governing the magnetic transition.
Main Methods:
- Synthesis and characterization of mixed composition LaFe(x)Co(2-x)P(2) (x ≤ 0.5) compounds.
- Single-crystal and powder X-ray and neutron diffraction for structural analysis.
- Magnetization, heat capacity, Mössbauer spectroscopy, and electronic band structure calculations for magnetic and electronic properties.
Main Results:
- Curie temperature decreases from 132 K in LaCo(2)P(2) to 91 K in LaFe(0.05)Co(1.95)P(2).
- Spin-glass-like behavior observed in LaFe(0.1)Co(1.9)P(2) and LaFe(0.2)Co(1.8)P(2), with no long-range magnetic ordering.
- Paramagnetic behavior observed in LaFe(0.3)Co(1.7)P(2) and LaFe(0.5)Co(1.5)P(2) down to 1.8 K.
- Unit cell parameters deviate from Vegard behavior; M-M distances decrease with increasing Fe content.
- Electronic structure calculations show reduced M-M interaction antibonding character and Fermi level shift, suppressing the Stoner criterion.
Conclusions:
- Ferromagnetic ordering in LaCo(2)P(2) is progressively suppressed by iron substitution.
- A transition from ferromagnetism to spin-glass-like behavior and finally to paramagnetism occurs with increasing Fe content.
- The observed magnetic evolution is attributed to changes in electronic band structure and M-M interactions upon aliovalent substitution.
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