Research areas

Strongly correlated oxides and multiferroic systems

The order or disorder of the spin and orbital degrees of freedom of electrons in transition metal oxides is responsible for a wide variety of phenomena [1]. For example, the colossal magnetoresistance (CMR) effect observed in manganese oxide compounds with an ABO3 perovskite structure (e.g. (La,Sr)MnO3 or (Pr,Ca)MnO3) results of the complex spin-orbital coupled state of the manganese lattice [2]. In materials with complex orbital order and/or spin structures, an electric polarization may be induced, making the material (in a large sense) magnetoelectric multiferroic [3]. Such materials display magnetoelectric effects, permitting e.g. the control of the magnetization of a material by means of an electric field or reciprocally the control of its polarization by means of a magnetic field, and are thus very attractive for application in many devices [4]. There are however few spintronic magnetoresistive oxides or magnetoelectric multiferroics which can be used at room temperature. We are thus investigating new materials, to be able to explore further, and extract new fundamental information on the mechanisms bringing forth those properties.

  1. “Complexity in Strongly Correlated Systems”, E. Dagotto, Science 309, 257 (2005).
  2. “Orbital Physics in Transition-Metal Oxides”, Y. Tokura and N. Nagaosa, Science 288, 462 (2000).
  3. “Classifying multiferroics: Mechanisms and effects ”, D. Khomskii, Physics 2, 20 (2009).
  4. "Advances in magnetoelectric multiferroics", N. Spaldin and R. Ramesh, Nature Materials 18, 203 (2019).

Some of our results can be found in the following publications:

Partial cation ordering, relaxor ferroelectricity and ferrimagnetism in Pb(Fe1-xYbx)2/3W1/3O3 solid solutions, S. A. Ivanov, D. C. Joshi, A. A. Bush, D. Wang, B. Sanyal, O. Eriksson, P. Nordblad, R. Mathieu, J. Appl. Phys. 128, 134102 (2020).

Cation ordering, ferrimagnetism and ferroelectric relaxor behavior in Pb(Fe1-xScx)2/3W1/3O3 solid solutions, S. A. Ivanov, P. Beran, A. A. Bush, T. Sarkar, S. Shafeie, D. Wang, B. Sanyal, O. Eriksson, M. Sahlberg, Ya. Kvashnin, R. Tellgren, P. Nordblad, R. Mathieu, Eur. Phys. J. B 92, 163 (2019).

Spin and dipole order in geometrically frustrated mixed-valence manganite Pb3Mn7O15, S. A. Ivanov, A. A. Bush, M. Hudl, A. I. Stash, G. André, R. Tellgren, V. M. Cherepanov, A. V. Stepanov, K. E. Kamentsev, Y. Tokunaga, Y. Taguchi, Y. Tokura, P. Nordblad, and R. Mathieu, J. Mater. Sci.: Mater. Electron. 27, 12562 (2016).

Successive phase transitions in the orthovanadate TmVO3, T. Sarkar, S. A. Ivanov, G. V. Bazuev, P. Nordblad and R. Mathieu, J. Phys. D: Appl. Phys. 48, 345003 (2015).

Crystal Structure and Antiferromagnetic Spin Ordering of LnFe2/3Mo1/3O3 (Ln = Nd, Pr, Ce, La) Perovskites, S. A. Ivanov, P. Beran, G. V.Bazuev, T. Ericsson, R. Tellgren, P. Anil Kumar, P. Nordblad, and R. Mathieu, Phys. Rev. B 91, 094418 (2015).

Mn2FeSbO6: a ferrimagnetic ilmenite and an antiferromagnetic perovskite, R. Mathieu, S. A. Ivanov, I. V. Solovyev, G. V. Bazuev, P. Anil Kumar, P. Lazor, and P. Nordblad, Phys. Rev. B 87, 014408 (2013).

Enhancement of antiferromagnetic interaction and transition temperature in M3TeO6 systems (M = Mn, Co, Ni, Cu), R. Mathieu, S. A. Ivanov, P. Nordblad, and M. Weil, Eur. Phys. J. B 86, 361 (2013).

Complex magnetism and magnetic field-driven electrical polarization in Co3TeO6, M. Hudl, R. Mathieu, S. A. Ivanov, M. Weil, V. Carolus, T. Lottermoser, M. Fiebig, Y. Tokunaga, Y. Taguchi, Y. Tokura, and P. Nordblad,  Phys. Rev. B 84, 180404(R) (2011).

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Magnetic nanoparticle systems and nanocomposites for spintronic and permanent magnet applications

Environment-friendly technologies implies an ever-increasing demand for permanent magnets [1]. It is difficult to optimize the performance of magnets in single phased materials as ideally both the saturation magnetization and coercivity of the material shall be maximized. The nanostructuring of magnetic materials in the form of nanocomposites comprising hard and soft magnetic phases with large staturation and large coercivity, respectively, shows a promising route to design new magnets [2]. Nanoparticles systems and nanocomposites may also be used to obtain novel spintronic materials by combining materials with different properties (e.g. ferromagnetic and ferroelectric [3]) on the nanoscale.

  1. Magnetic Materials and Devices for the 21st Century: Stronger, Lighter, and More Energy Efficient, O. Gutfleisch et al., Adv. Mater. 23, 821 (2011).
  2. Prospects for nanoparticle-based permanent magnets, B. Balamurugan, D. J. Sellmyer, G. C. Hadjipanayis, and R. Skomski, Scripta Materialia 67, 542 (2012).
  3. “Multiferroic BaTiO3-CoFe2O4 nanostructures”, H. Zheng et al., Science 303, 661 (2004).

Some of our results can be found in the following publications:

Complex correlations between microstructure and magnetic behavior in SrFe12O19 hexaferrite nanoparticles, P. Maltoni, S. A. Ivanov, G. Barucca, G. Varvaro, D. Peddis, R. Mathieu, Sci. Rep. 11, 23307 (2021).

Tuning the magnetic properties of hard-soft SrFe12O19/CoFe2O4 nanostructures via composition/interphase coupling, P. Maltoni, T. Sarkar, G. Barucca, G. Varvaro, F. Locardi, D. Peddis, and R. Mathieu, J. Phys. Chem. C 125, 5927 (2021).

Exploring the magnetic properties and magnetic coupling in SrFe12O19/Co1-xZnxFe2O4 nanocomposites, P. Maltoni, T. Sarkar, G. Barucca, G. Varvaro, D. Peddis, and R. Mathieu, J. Magn. Magn. Mater. 535, 168095 (2021).

Towards bi-magnetic nanocomposites as permanent magnets through the optimization of the synthesis and magnetic properties of SrFe12O19 nanocrystallites, P. Maltoni, T. Sarkar, G. Varvaro, G. Barucca, S. A. Ivanov, D. Peddis, and R Mathieu, J. Phys. D: Appl. Phys. 54, 124004 (2021).

Tunable single-phase magnetic behavior in chemically synthesized AFeO3 - MFe2O4 (A = Bi or La, M = Co or Ni) nanocomposites, T. Sarkar, G. Muscas, G. Barucca, F. Locardi, G. Varvaro, D. Peddis, R. Mathieu, Nanoscale 10, 22990 (2018).

Designing new manganite/ferrite nanocomposites, G. Muscas, P. Anil Kumar, G. Barucca, G. Concas, G. Varvaro, R. Mathieu, and D. Peddis, Nanoscale 8, 2081 (2016).

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Magnetic quasicrystals

Quasicrystals have long-ranged aperiodic atomic structures whose characteristics and properties are yet to be understood [1]. Information of these properties may be extracted by collecting data on quasicrystals, as well as approximants of quasicrystals, which are periodic crystals with similar local structure. Quasicrystals and approximant crystals are mostly intermetallic systems, which may include magnetic rare earths such as Gd, Ho or Tb, and display specific magnetic properties[1,2]. The exact origin and nature of the magnetic interaction in these systems in not completely understood; see also the project description at: for more information.

  1. Magnetism in icosahedral quasicrystals: current status and open questions, A. Goldman, Sci. Technol. Adv. Mater. 15, 044801 (2014).
  2. Whirling spin order in the quasicrystal approximant Au72Al14Tb14, T. J. Sato et al., Phys. Rev. B 100, 054417 (2019).

Some of our results can be found in the following publications:

Nonequilibrium dynamical behavior in noncoplanar magnets with chiral spin texture, T. Shiino, F. Denoel, G. H. Gebresenbut, C. Pay Gomez, P. Nordblad, R. Mathieu, Phys. Rev. B Letter 195,  L180409 (2022).

Singular magnetic dilution behavior in a quasicrystal approximant, T. Shiino, F. Denoel, G. H. Gebresenbut, D. C. Joshi, Y.-C. Huang, C. Pay Gomez, U. Häussermann, A. Rydh, R. Mathieu, Phys. Rev. B. 104, 224411 (2021).

Superconductivity at 1 K in Y–Au–Si quasicrystal approximants, T. Shiino, G. H. Gebresenbut, F. Denoel, R. Mathieu, U. Häussermann, and A. Rydh, Phys. Rev. B 103, 054510 (2021).

Atomic scale tuning of Tsai-type clusters in RE-Au-Si systems (RE = Gd, Tb, Ho), G. Gebresenbut, T. Shiino, D. Eklöf, D. C. Joshi, F. Denoel, R. Mathieu, U. Häussermann, C. Pay Gomez, Inorg. Chem. 59, 9152 (2020).

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Spin glasses and superspin glasses

Spin glasses are non equilibrium systems with specific magnetic properties [1,2]. For example after a rapid cooling of a material into its glassy phase, the magnetization of a spin glass will evolve with time in a characteristic way, as a consequence of the slow reorganization of its spin configuration triggered by the temperature perturbation [1]. Spin glasses may hence "age", but also "remember" (memory effects) and "forget" (rejuvenation effects) at the same time [1] and specific measurement protocols are required to investigate their dynamical properties [1] and phase transitions [2] . Interestingly, glassy effects and spin glass phases are ubiquitous and observed in a wide variety of materials [2], from metallic alloys to transition metal / strongly correlated oxides, geometrically frustrated systems, magnetic quasicrystals, and chiral-glass superconductors. They also appear in e.g. dipolarly interacting magnetic nanoparticle systems; defining superspins and superspin glasses [1].

  1. Competing interaction in magnets: the root of ordered disorder or only frustration?, P. Nordblad, Phys. Scr. 88, 058301 (2013).
  2. Spin glasses, H. Kawamura and T. Tanuguchi, Handbook of Magnetic Materials, 24, 1-137 (2015).

Some of our results can be found in the following publications:

Memory and superposition in a superspin glass, D. Peddis, K. N. Trohidou, M. Vasilakaki, G. Margaris, M. Bellusci, F. Varsano, M. Hudl, N. Yaacoub, D. Fiorani, P. Nordblad, and R. Mathieu, Sci. Rep. 11, 7743 (2021).

Memory and rejuvenation in a quasicrystal, D. C. Joshi, G. Gebresenbut, C. Pay Gomez, R. Mathieu, Europhys. Lett. (EPL) 132, 27002 (2020).

Tunable exchange bias in dilute magnetic alloys - chiral spin glasses, M. Hudl, R. Mathieu, and P. Nordblad, Sci. Rep. 6, 19964 (2016).

Effects of the individual particle relaxation time on superspin glass dynamics, M. S. Andersson, J. A. De Toro, S. S. Lee, P. S. Normile, P. Nordblad, and R. Mathieu, Phys. Rev. B 93, 054407 (2016).

Phase transition in a super superspin glass, R. Mathieu, J. A. De Toro, D. Salazar, S. S. Lee, J. L. Cheong, and P. Nordblad, Europhys. Lett. (EPL) 102, 67002 (2013).

Isothermal remanent magnetization and the spin dimensionality of spin glasses, R. Mathieu, M. Hudl, P. Nordblad, Y. Tokunaga, Y. Kaneko, Y. Tokura, H. Aruga Katori, and A. Ito, Philos. Mag. Lett. 90, 723 (2010).

Logarithmic growth law in the two-dimensional Ising spin glass state resulting from the electron doping in single-layered manganites, R. Mathieu, J. P. He, Y. Kaneko, H. Yoshino, A. Asamitsu, and Y. Tokura, Phys. Rev. B 76, 014436 (2007).

Eu0.5Sr1.5MnO4: a three-dimensional XY spin glass, R. Mathieu, A. Asamitsu, Y. Kaneko, J. P. He, and Y. Tokura, Phys. Rev. B 72, 014436 (2005).

Memory and superposition in a spin glass, R. Mathieu, P. Jönsson, D. N. H. Nam, and P. Nordblad, Phys. Rev. B 63, 092401 (2001).

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Last modified: 2022-05-17