Young B-MRS member receives 4 awards from international scientific societies in 2017.

Navadeep Shrivastava at the E-MRS Spring Meeting 2017 presenting the awarded poster.
Navadeep Shrivastava at the E-MRS Spring Meeting 2017 presenting the awarded poster.

So far this year, B-MRS member Navadeep Shrivastava has won four awards for his work on materials with magnetic and luminescent properties developed in the context of his doctoral research being conducted at the Federal University of Maranhão (UFMA) under the guidance of Professor Surender Kumar Sharma.

In February, Shrivastava was selected to receive a registration exemption at the E-MRS 2017 Spring Meeting, within an existing agreement between B-MRS and the European Materials Research Society (E-MRS). The award allowed the participation of the doctoratal student in the event, which was held in Strasbourg (France) from 22 to 26 May 2017.

At the E-MRS event, Shrivastava won an award for the poster he presented at the symposium entitled “Luminescence and Magnetic Behavior of Color Tuned LaF3:RE3+  (RE= Ce, Gd, Eu) Nanoparticles”. In addition, he presented another contribution at symposium V (“Green emitting magneto-luminescent iron-oxide/ZnS coated by codoped lanthanum fluoride nanomaterials”), which drew the attention of the audience, initiated a collaborative relationship with a group from the Université de Strasbourg (France) and expanded his network of professional contacts. “I want to express my gratitude for the opportunity to participate in the E-MRS 2017 Spring Meeting,” says Shrivastava.

In third place, the doctoral student was one of the winners of the 2017 Bernhard Gross Award, awarded by SBPMat to the best works presented by students at the annual events of the society. Shrivastava was awarded for the work “Facile synthesis and magneto-luminescence study of aliance of iron oxide and NaGdF4:RE3+ into nanoentity”, presented in an oral session at symposium B. The award was delivered on September 14 this year in the city of Gramado, during the closing ceremony of the XVI B-MRS Meeting.

Finally, the UFMA PhD student has just been selected to receive a travel assistance from the IEEE Magnetics Society to present two papers at the 62nd edition of the International Conference on Magnetism and Magnetic Materials, called MMM 2017, to be held in Pittsburgh in November of this year.

Featured paper: Phonons coupled to magnetic order in the origin of ferroelectricity.

Paper:  Spin-phonon and magnetostriction phenomena in CaMn7O12 helimagnet probed by Raman spectroscopy. Nonato, A.; Araujo, B.S.; Ayala, AP; Maciel, AP; Yanez-Vilar, S.; Sanchez-Andujar, M.; Senaris-Rodriguez, MA; Paschoal, CWA. Applied Physics Letters 105, 222902 (2014); DOI: 10.1063/1.4902234.

Through a study based, mainly, on the technique of Raman spectroscopy, resarchers from Brazil, in collaboration with scientists from Spain, progressed in the understanding of the mechanisms involved in the generation of magnetically induced ferroelectricity (electric polarization that occurs in some materials with spiral magnetic order, even when they are not under the action of electric fields) in the CMO compound.

CMO, which formula is CaMn7O12, is a ceramic oxide of perovskite structure that presents, simultaneously, at low temperatures, ferroelectricity and anti-ferromagnetism.

In addition to contribute to the advance of fundamental science, the work, which results were recently published in Applied Physics Letters (APL) journal, opens possibilities to the creation of new materials which polarization may be controlled through magnetic fields. Such materials could be applied, for example, in new spintronic devices for data storage, faster and that consume less energy.

The study was performed during Ariel Nonato Almeida de Abreu Silva’s PhD research work, advised by Carlos William de Araujo Paschoal, Professor at the Physics department of the Brazilian Federal University of Maranhão (UFMA), where he leads a research group in dielectric and vibrational properties. “The idea arose out of the search for multiferroic and magnetoelectric materials that allow for a control of the electric polarization upon replacements”, says professor Araujo Paschoal, who signs the article together with other seven researchers. According to him, CMO was chosen because it presents a rich diagram of phases (magnetic, structural, and charge order), and because it is unique in the mechanisms that generate ferroelectricity from its magnetic properties.

Among CMO’s particularities, there is a magnetic transition, which occurs at 90K (around -180°C), where the compound passes from paramagnetic phase to anti-ferromagnetic phase, inducing a giant ferroelectricity.

In the study that generated APL’s paper, Ariel and his advisor analyzed in details the Raman spectra of CMO samples at several temperatures (from 300 K to 10K) to investigate the collective vibrations of the atoms of the crystalline lattice (phonons) and their relation with magnetic order. Among other results, they were able to prove that, at 90 K, the phonons showed an unusual behavior due to the coupling to magnetic order.

“The main contribution of this work is to help in the understanding of how the phonons couple to the magnetic order in CaMn7O12(CMO). It is, with no doubt, a great step that allows us to progress in the understanding of the origin of the induced electric polarization in CMO, which is also a subject of great discussion in literature”, affirms Paschoal.

Raman spectrum of CMO at 10 K. The inset shows the ferroaxial coupling of the magnetic helix with the global rotation of the structure described by the axial vector A.

The experimental work of this study started with the synthesis of the samples, which was done at Universidad de A Coruña (Spain), where Ariel was performing a doctoral fellowship period under the supervision of Professor Maria Antonia Señaris Rodriguez. After that, at Universidad de Santiago de Compostela, a series of magnetic measures was performed. Finally, the Raman spectroscopy measures were carried out in the Laboratory of Light Scattering at the Federal University of Ceará, in cooperation with professor Alejandro Pedro Ayala, and in the Physics department of UFMA itself, in the Laboratory of Vibrational Spectroscopy and Impedance (LEVI).

The work was funded by Brazilian federal agencies (CNPq and CAPES) and state agencies (FUNCAP e FAPEMA, from Ceará and Maranhão states, respectively), and by entities from Europe.