[Paper Review] Investigation of intrinsic magnetodielectric effect in La2CoMnO6: Role of magnetic disorder

J. Krishna Murthya, K. Devi Chandrasekhar S. Murugavel+1 more|arXiv (Cornell University)|Nov 10, 2014

Magnetic and transport properties of perovskites and related materials4 references3 citations

TL;DR

This study investigates the intrinsic magnetodielectric (MD) effect in B-site-ordered La2CoMnO6 (LCMO), revealing a large MD effect of 65% at 100 kHz under a 5 T magnetic field. The research disentangles intrinsic contributions from spin-lattice coupling via Raman spectroscopy and extrinsic effects from magnetic disorder and carrier doping, showing that disorder suppresses intrinsic polarization and dominates MD and magnetoresistance responses.

ABSTRACT

We present a large magnetodielectric (MD) effect of 65 % at 100 kHz with 5 T field in B-site ordered La2CoMnO6 (LCMO) polycrystalline sample. Frequency and temperature dependent impedance and dielectric studies under magnetic field divulge both intrinsic and extrinsic origins for the observed MD effect. The temperature dependent Raman spectroscopy measurement has shown spin-lattice coupling that supports the intrinsic origin of the observed large MD response in LCMO. Extrinsic contributions to MD response mainly originate from disorder and interface effects; here, we signify this by hole carrier (Sr) doping at the A-site of the ordered LCMO sample. The comparison study has disclosed that with the disorder, the intrinsic polarization due to asymmetric hopping decreases significantly, and the disorder induced transport dominates in both MD and magnetoresistance behaviour with close resemblance.

Motivation & Objective

• To understand the origin of the large magnetodielectric effect in B-site-ordered La2CoMnO6.
• To distinguish between intrinsic and extrinsic contributions to the MD effect in LCMO.
• To examine the impact of magnetic disorder and A-site Sr doping on MD and magnetoresistance behavior.
• To establish the role of spin-lattice coupling in mediating intrinsic MD response through Raman spectroscopy.
• To clarify how disorder-induced carrier transport dominates over intrinsic polarization in MD response.

Proposed method

• Conducting frequency- and temperature-dependent impedance and dielectric spectroscopy under applied magnetic fields to probe MD response.
• Performing temperature-dependent Raman spectroscopy to detect spin-lattice coupling in LCMO.
• Introducing Sr doping at the A-site to induce magnetic and structural disorder in the B-site-ordered LCMO system.
• Comparing MD and magnetoresistance responses in pristine and doped LCMO samples to isolate extrinsic contributions.
• Analyzing dielectric relaxation and conductivity behavior to identify dominant transport mechanisms.
• Using the MD effect magnitude (65% at 100 kHz, 5 T) as a quantitative benchmark for intrinsic vs. extrinsic contributions.

Experimental results

Research questions

• RQ1 What is the origin of the large magnetodielectric effect in B-site-ordered La2CoMnO6?
• RQ2 How does magnetic disorder influence the intrinsic and extrinsic components of the MD effect?
• RQ3 To what extent does spin-lattice coupling contribute to the intrinsic MD response in LCMO?
• RQ4 How does A-site Sr doping alter the MD and magnetoresistance behavior in LCMO?
• RQ5 Why does disorder dominate the MD response despite the presence of intrinsic polarization mechanisms?

Key findings

• A large intrinsic magnetodielectric effect of 65% was observed at 100 kHz under a 5 T magnetic field in B-site-ordered La2CoMnO6.
• Temperature-dependent Raman spectroscopy confirmed spin-lattice coupling, supporting the intrinsic origin of the MD effect.
• Extrinsic contributions to the MD effect arise primarily from magnetic disorder and interface effects.
• Sr doping at the A-site significantly reduces intrinsic polarization due to asymmetric electron hopping.
• Disorder-induced carrier transport dominates both MD and magnetoresistance responses, showing close resemblance in behavior.
• The study confirms that while intrinsic MD exists, extrinsic effects from disorder are the dominant contributors in polycrystalline LCMO samples.