PMID- 30324204
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20181030
LR  - 20181030
IS  - 1463-9084 (Electronic)
IS  - 1463-9076 (Linking)
VI  - 20
IP  - 41
DP  - 2018 Nov 7
TI  - Magnetic studies of layer-by-layer assembled polyvinyl alcohol/iron oxide 
      nanofilms.
PG  - 26696-26709
LID - 10.1039/c8cp05404e [doi]
AB  - This study reports on investigation of the magnetic properties of layer-by-layer 
      (LbL) assembled nanofilms comprising polyvinyl alcohol (PVA) and citrate-coated 
      magnetite (cit-MAG) nanoparticles deposited onto silicon (SF sample) and glass 
      (GF sample) substrates. DC magnetization measurements were performed over the 
      temperature range of 4 K to 300 K, in the applied magnetic field range of +/-60 
      kOe. The magnetic data of the as-synthesized cit-MAG nanoparticles (F sample) are 
      also collected for comparison. The three as-fabricated samples reveal perfect 
      superparamagnetic (SPM) behavior only around room temperature; at temperatures 
      lower than 200 K the SPM scaling is not observed and all samples behave as 
      interacting superparamagnetic (ISPM) materials. The evolution from the ISPM to 
      the SPM regime is marked by a steady decrease in the hysteretic properties of all 
      samples, with the temperature-dependence of the coercivity decreasing slower than 
      the T(1/2) behavior predicted for non-interacting superparamagnetic particles. 
      The modified Bloch's law used to assess information on nanoparticles' surface 
      spins gives the Bloch's exponent close to 2 (for the F and SF samples) and close 
      to 1 (for the GF sample). Interestingly, the surface spin freezing temperature 
      (T(f)) is 8 +/- 1 K for all samples. The magnetic behavior of all three samples can 
      be described within the model picture of a core-shell structure for the cit-MAG 
      nanoparticles; the core comprising magnetically-ordered spins whereas the shell 
      behaving as a spin-glass-like system. However, the contribution of the shell 
      magnetism to the effective magnetic properties is much more evident in the GF 
      sample in which magnetic dipole-dipole interaction is three-times weaker than in 
      the SF sample and two times weaker than in the F sample. In contrast, the strong 
      magnetic dipole-dipole interaction in the SF sample affects the surface spins, 
      hindering the onset of magnetically-ordered regions in the nanoparticle's shell, 
      making the surface magnetism contribution negligible. The LbL-fabricated 
      nanofilms herein reported and the presented analysis of their magnetic properties 
      we envisage can support the engineering of magnetic nanofilms for multiple 
      applications.
FAU - Mosiniewicz-Szablewska, Ewa
AU  - Mosiniewicz-Szablewska E
AUID- ORCID: 0000-0003-1707-1086
AD  - Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 
      Warsaw, Poland. mosin@ifpan.edu.pl.
FAU - Clavijo, Antonia R
AU  - Clavijo AR
AD  - Universidade de Brasilia, Instituto de Fisica, Brasilia DF 70910-900, Brazil.
FAU - Castilho, Ana P O R
AU  - Castilho APOR
AD  - Universidade de Brasilia, Instituto de Fisica, Brasilia DF 70910-900, Brazil.
FAU - Paterno, Leonardo G
AU  - Paterno LG
AUID- ORCID: 0000-0001-7716-0318
AD  - Universidade de Brasilia, Instituto de Quimica, Brasilia DF 70910-900, Brazil.
FAU - Pereira-da-Silva, Marcelo A
AU  - Pereira-da-Silva MA
AD  - Institute of Physics of Sao Carlos, IFSC/USP, Sao Carlos SP, Brazil and Paulista 
      Central University Center, UNICEP, Sao Carlos SP, Brazil.
FAU - Wieckowski, Jaroslaw
AU  - Wieckowski J
AD  - Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 
      Warsaw, Poland. mosin@ifpan.edu.pl.
FAU - Soler, Maria A G
AU  - Soler MAG
AD  - Universidade de Brasilia, Instituto de Fisica, Brasilia DF 70910-900, Brazil.
FAU - Morais, Paulo C
AU  - Morais PC
AD  - Universidade de Brasilia, Instituto de Fisica, Brasilia DF 70910-900, Brazil and 
      Universidade Catolica de Brasilia, Programa de Pos-Graduacao em Ciencias 
      Genomicas e Biotecnologia, Brasilia DF 70790-160, Brazil.
LA  - eng
PT  - Journal Article
DEP - 20181016
PL  - England
TA  - Phys Chem Chem Phys
JT  - Physical chemistry chemical physics : PCCP
JID - 100888160
EDAT- 2018/10/17 06:00
MHDA- 2018/10/17 06:01
CRDT- 2018/10/17 06:00
PHST- 2018/10/17 06:00 [pubmed]
PHST- 2018/10/17 06:01 [medline]
PHST- 2018/10/17 06:00 [entrez]
AID - 10.1039/c8cp05404e [doi]
PST - ppublish
SO  - Phys Chem Chem Phys. 2018 Nov 7;20(41):26696-26709. doi: 10.1039/c8cp05404e. Epub 
      2018 Oct 16.