Hematite: Morin temperature of nanoparticles with different size

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388980%3A_____%2F19%3A00505935" target="_blank" >RIV/61388980:_____/19:00505935 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11320/19:10388255 RIV/68378271:_____/19:00538738

Výsledek na webu

<a href="http://hdl.handle.net/11104/0297265" target="_blank" >http://hdl.handle.net/11104/0297265</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.jmmm.2018.11.126" target="_blank" >10.1016/j.jmmm.2018.11.126</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Hematite: Morin temperature of nanoparticles with different size

Popis výsledku v původním jazyce

A spin-reorientation transition from a weakly ferromagnetic (WF) to an antiferromagnetic (AF) spin ordering in hematite (α-Fe2O3) during cooling occurs at Morin temperature (TM∼264 K for bulk). The transition is strongly size dependent and TM generally decreases with the decreasing volume of the particles. For particles smaller than approximately ∼20 nm, the Morin transition may be even suppressed and disappears entirely as near-surface spins deviate strongly from the antiferromagnetic easy axis. We report an investigation on nanoparticles prepared by hydrothermal method and sol–gel technique (in silica) of pure α-Fe2O3 phase as confirmed by XRD (space group R-3c, lattice parameters a = 5.038(2) Å c = 13.772(12) Å) differing in the median size derived by TEM: 5.6 nm, 26 nm, 42 nm and 103 nm. By means of Mössbauer spectra acquired between 4.2 and 300 K, we determined the relative concentrations of magnetic phases (WF and AF) within the 57Fe enriched sample and searched for the best finite-scaling theoretical model (mean-field, 3D Heisenberg, Ising) describing the derived size dependence of Morin temperature of the nanoparticles with a log-normal size distribution. The comparison of relevant parameters derived from the fit of experimental data by theoretical model is consistent with the 3D Heisenberg model with scaling parameter λ = 1.4, Morin temperature of bulk material TM(∞) = 265(1) K and correlation length ξ0 = 8.1(2) nm or Ising model with λ = 1.6, TM(∞) = 265(1) K and ξ0 = 9.4(2) nm.

Název v anglickém jazyce

Hematite: Morin temperature of nanoparticles with different size

Popis výsledku anglicky

A spin-reorientation transition from a weakly ferromagnetic (WF) to an antiferromagnetic (AF) spin ordering in hematite (α-Fe2O3) during cooling occurs at Morin temperature (TM∼264 K for bulk). The transition is strongly size dependent and TM generally decreases with the decreasing volume of the particles. For particles smaller than approximately ∼20 nm, the Morin transition may be even suppressed and disappears entirely as near-surface spins deviate strongly from the antiferromagnetic easy axis. We report an investigation on nanoparticles prepared by hydrothermal method and sol–gel technique (in silica) of pure α-Fe2O3 phase as confirmed by XRD (space group R-3c, lattice parameters a = 5.038(2) Å c = 13.772(12) Å) differing in the median size derived by TEM: 5.6 nm, 26 nm, 42 nm and 103 nm. By means of Mössbauer spectra acquired between 4.2 and 300 K, we determined the relative concentrations of magnetic phases (WF and AF) within the 57Fe enriched sample and searched for the best finite-scaling theoretical model (mean-field, 3D Heisenberg, Ising) describing the derived size dependence of Morin temperature of the nanoparticles with a log-normal size distribution. The comparison of relevant parameters derived from the fit of experimental data by theoretical model is consistent with the 3D Heisenberg model with scaling parameter λ = 1.4, Morin temperature of bulk material TM(∞) = 265(1) K and correlation length ξ0 = 8.1(2) nm or Ising model with λ = 1.6, TM(∞) = 265(1) K and ξ0 = 9.4(2) nm.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10402 - Inorganic and nuclear chemistry

Projekt

<a href="/cs/project/GA16-04340S" target="_blank" >GA16-04340S: Oxidové nanomagnety, jejich vlastnosti a interakce s biologickými systémy</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Journal of Magnetism and Magnetic Materials

ISSN

0304-8853

e-ISSN

—

Svazek periodika

475

Číslo periodika v rámci svazku

APR

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

9

Strana od-do

611-619

Kód UT WoS článku

000458152000087

EID výsledku v databázi Scopus

2-s2.0-85057739897