Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub>
The antiferromagnetic (AFM) transition of the normal ZnFe<sub>2</sub>O<sub>4</sub> has been intensively investigated with results showing a lack of long-range order, spin frustrations, and a “hidden” entropy in the calorimetric properties for inversion degrees δ ≈ 0 or δ = 0....
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2022-02-01
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| author | Miguel Angel Cobos Antonio Hernando José Francisco Marco Inés Puente-Orench José Antonio Jiménez Irene Llorente Asunción García-Escorial Patricia de la Presa |
| author_facet | Miguel Angel Cobos Antonio Hernando José Francisco Marco Inés Puente-Orench José Antonio Jiménez Irene Llorente Asunción García-Escorial Patricia de la Presa |
| author_sort | Miguel Angel Cobos |
| collection | DOAJ |
| description | The antiferromagnetic (AFM) transition of the normal ZnFe<sub>2</sub>O<sub>4</sub> has been intensively investigated with results showing a lack of long-range order, spin frustrations, and a “hidden” entropy in the calorimetric properties for inversion degrees δ ≈ 0 or δ = 0. As δ drastically impacts the magnetic properties, it is logical to question how a δ value slightly different from zero can affect the magnetic properties. In this work, (Zn<sub>1-δ</sub>Fe<sub>δ</sub>)[Zn<sub>δ</sub>Fe<sub>2-δ</sub>]O<sub>4</sub> with δ = 0.05 and δ = 0.27 have been investigated with calorimetry at different applied fields. It is shown that a δ value as small as 0.05 may affect 40% of the unit cells, which become locally ferrimagnetic (FiM) and coexists with AFM and spin disordered regions. The spin disorder disappears under an applied field of 1 T. Mossbauer spectroscopy confirms the presence of a volume fraction with a low hyperfine field that can be ascribed to these spin disordered regions. The volume fractions of the three magnetic phases estimated from entropy and hyperfine measurements are roughly coincident and correspond to approximately 1/3 for each of them. The “hidden” entropy is the zero point entropy different from 0. Consequently, the so-called “hidden” entropy can be ascribed to the frustrations of the spins at the interphase between the AFM-FiM phases due to having δ ≈ 0 instead of ideal δ = 0. |
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| id | doaj.art-5272235146994d69aa2e8f2d34b485c3 |
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| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-09T23:34:02Z |
| publishDate | 2022-02-01 |
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| spelling | doaj.art-5272235146994d69aa2e8f2d34b485c32023-11-23T17:03:56ZengMDPI AGMaterials1996-19442022-02-01153119810.3390/ma15031198Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub>Miguel Angel Cobos0Antonio Hernando1José Francisco Marco2Inés Puente-Orench3José Antonio Jiménez4Irene Llorente5Asunción García-Escorial6Patricia de la Presa7Instituto de Magnetismo Aplicado (UCM-ADIF), CSIC, 28260 Las Rozas, SpainInstituto de Magnetismo Aplicado (UCM-ADIF), CSIC, 28260 Las Rozas, SpainInstituto de Química Física Rocasolano, 28006 Madrid, SpainInstitut Laue-Langevin, CEDEX 09, 38042 Grenoble, FranceCentro Nacional de Investigaciones Metalúrgicas (CENIM), CSIC, 28040 Madrid, SpainCentro Nacional de Investigaciones Metalúrgicas (CENIM), CSIC, 28040 Madrid, SpainCentro Nacional de Investigaciones Metalúrgicas (CENIM), CSIC, 28040 Madrid, SpainInstituto de Magnetismo Aplicado (UCM-ADIF), CSIC, 28260 Las Rozas, SpainThe antiferromagnetic (AFM) transition of the normal ZnFe<sub>2</sub>O<sub>4</sub> has been intensively investigated with results showing a lack of long-range order, spin frustrations, and a “hidden” entropy in the calorimetric properties for inversion degrees δ ≈ 0 or δ = 0. As δ drastically impacts the magnetic properties, it is logical to question how a δ value slightly different from zero can affect the magnetic properties. In this work, (Zn<sub>1-δ</sub>Fe<sub>δ</sub>)[Zn<sub>δ</sub>Fe<sub>2-δ</sub>]O<sub>4</sub> with δ = 0.05 and δ = 0.27 have been investigated with calorimetry at different applied fields. It is shown that a δ value as small as 0.05 may affect 40% of the unit cells, which become locally ferrimagnetic (FiM) and coexists with AFM and spin disordered regions. The spin disorder disappears under an applied field of 1 T. Mossbauer spectroscopy confirms the presence of a volume fraction with a low hyperfine field that can be ascribed to these spin disordered regions. The volume fractions of the three magnetic phases estimated from entropy and hyperfine measurements are roughly coincident and correspond to approximately 1/3 for each of them. The “hidden” entropy is the zero point entropy different from 0. Consequently, the so-called “hidden” entropy can be ascribed to the frustrations of the spins at the interphase between the AFM-FiM phases due to having δ ≈ 0 instead of ideal δ = 0.https://www.mdpi.com/1996-1944/15/3/1198zinc ferritehidden entropyspin disorderneutron diffractioncalorimetry |
| spellingShingle | Miguel Angel Cobos Antonio Hernando José Francisco Marco Inés Puente-Orench José Antonio Jiménez Irene Llorente Asunción García-Escorial Patricia de la Presa Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub> Materials zinc ferrite hidden entropy spin disorder neutron diffraction calorimetry |
| title | Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub> |
| title_full | Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub> |
| title_fullStr | Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub> |
| title_full_unstemmed | Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub> |
| title_short | Unveiling the Hidden Entropy in ZnFe<sub>2</sub>O<sub>4</sub> |
| title_sort | unveiling the hidden entropy in znfe sub 2 sub o sub 4 sub |
| topic | zinc ferrite hidden entropy spin disorder neutron diffraction calorimetry |
| url | https://www.mdpi.com/1996-1944/15/3/1198 |
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