HYBRID EVENT: You can participate in person at Orlando, USA or Virtually from your home or work.

6th edition of World Nanotechnology Conference

April 24-25, 2023

April 24 -26, 2023 | Orlando, USA
World Nano 2022

Hydrothermally synthesized novel delta-MnO2 nanowhiskers: Microstructure and magnetic properties

Chandana Rath, Speaker at Nanoscience conferences
Indian Institute of Technology (BHU), India
Title : Hydrothermally synthesized novel delta-MnO2 nanowhiskers: Microstructure and magnetic properties

Abstract:

We will discuss about one of the novel 2D monoclinic, P63/mnm, δ-MnO2 phase which were synthesized in the form of nanowhiskers through a simple and facile hydrothermal route under the optimized condition without using any template. The X-ray diffraction pattern showed the formation of the δ phase of MnO2 which was further confirmed from Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. Transmission electron micrograph revealed nanowhiskers of diameter ~7 nm and high- resolution TEM and SAED pattern demonstrated the interplanar spacing and distinguished diffraction rings corresponding to the monoclinic phase of δ-MnO2. Temperature dependent magnetization showed magnetic transition to paramagnetic phase at 13.2K which decreased to lower temperature with increasing the applied field. Temperature dependent susceptibility after fitted with Curie-Weiss law confirmed the strong antiferromagnetic ordering and high effective magnetic moment than that of Mn4+ present in δ-MnO2. A large effective magnetic moment is attributed to the presence of both Mn3+ and Mn4+ as confirmed from XPS. Reduced valency of Mn from 4+ to 3+ is accompanied with oxygen vacancies giving the exact composition as MnO1.58. The dynamic magnetic properties of δ-MnO2 nanowhiskers investigated using frequencydependent ac susceptibility fitted with various phenomenological models like Vogel-Fulcher law and power law clearly indicates the existence of the interacting spin clusters which freezes at ~ 11.2 K. Time dependence of thermoremanent magnetization, fitted well with stretched exponential function, supports the existence of relaxing spin clusters. Thus, spin glass relaxation in δ-MnO2 nanowhiskers was attributed to the interaction between Mn4+ and Mn3+ which results in an intrinsic magnetic frustration and weak ferromagnetism with finite coercivity below Tf.

Audience take-away:

  • Can use the unique synthesis technique.
  • Synthesize different dimension materials like nanowires of various aspect ratio, nanoparticles of various sizes and quantum dots.
  • Vary the shapes from spherical to non-spherical.
  • Magnetic properties can vary from super-paramagnetic to ferromagnetic depending on its size and shape.
  • In job requirement if anything required for varying the size of particle from nanosize to micron size then this method can be used.
  • Certainly, they can use this unique technique for other materials as well as we do in our laboratory.
  • Many unusual properties one could obtain through this technique for example we observe coercivity of ~4-6 kOe in an antiferromagnetic pseudocubic shape hematitite particles of different sizes.

Biography:

Dr. Chandana Rath received her Ph.D. degree in Physics from Utkal University, India and was a Post Doctoral fellow in University of Girona, Spain for 2 years. Her area of Research is Nanomagnetics , Multiferroics, Ion Irradiation, Semiconducting Nanostructured Materials. She has gained distinctions as Women Achiever in STEM in 2021, MRSI MEDAL 2015 from Materials Society of India, Young Researcher Award-1998 in IUMRS-ICA, India. She has completed several national projects and an international project from National Foundries of Fine Analysis, Europe. She has published three national patents and published more than 100 research articles in SCI(E) journals.

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