<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>1665-3521</journal-id>
<journal-title><![CDATA[Superficies y vacío]]></journal-title>
<abbrev-journal-title><![CDATA[Superf. vacío]]></abbrev-journal-title>
<issn>1665-3521</issn>
<publisher>
<publisher-name><![CDATA[Sociedad Mexicana de Ciencia y Tecnología de Superficies y Materiales A.C.]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1665-35212005000100011</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Mediciones del perfil de absorción de potencia a microondas en materiales ferroeléctricos y magnetoferroeléctricos]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Alvarez]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Zamorano]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Font]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Portelles]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
<xref ref-type="aff" rid="Aaf"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Román]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Castellanos]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Heiras]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Instituto Politécnico Nacional Escuela Superior de Física y Matemáticas Departamento de Ciencias de los Materiales]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Mexico</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Instituto Politécnico Nacional Escuela Superior de Física y Matemáticas Departamento de Física]]></institution>
<addr-line><![CDATA[ México, DF]]></addr-line>
<country>Mexico</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Universidad de la Habana Facultad de Física Departamento de Física Aplicada]]></institution>
<addr-line><![CDATA[La Habana ]]></addr-line>
<country>Cuba</country>
</aff>
<aff id="Af4">
<institution><![CDATA[,Universidad Nacional Autónoma de México Facultad de Química ]]></institution>
<addr-line><![CDATA[ México DF]]></addr-line>
<country>Mexico</country>
</aff>
<aff id="Af5">
<institution><![CDATA[,Universidad Nacional Autónoma de México Centro de Ciencias de la Materia Condensada ]]></institution>
<addr-line><![CDATA[Ensenada Baja California]]></addr-line>
<country>Mexico</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2005</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2005</year>
</pub-date>
<volume>18</volume>
<numero>1</numero>
<fpage>11</fpage>
<lpage>15</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S1665-35212005000100011&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S1665-35212005000100011&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S1665-35212005000100011&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen En este trabajo se reporta el perfil de absorción no-resonante de microondas como función de la temperatura, experimentalmente denominado MAMMAS (Magnetically Modulated Microwave Absorption Spectroscopy). El registro de frecuencias es de 8.8-9.8 GHz (Banda X) en materiales ferroeléctricos BaTiO3 (BT) y PbTiO3 (PT), y magnetoferroeléctricos YMnO3 (YM) y Pb(Fe1/2Nb1/2)O3 (PFN) en polvo. El perfil MAMMAS de los cerámicos BT y PT son debidos a procesos de absorción de microondas asociados con los dipolos eléctricos del material. En el perfil MAMMAS de los magnetoferroeléctricos YM y PFN se detecta la transición para- antiferromagnética, y solamente para el PFN se obtuvo la transición ferro-paraeléctrica; en el perfil MAMMAS se logra distinguir procesos de absorción asociados a dipolos eléctricos o dipolos magnéticos. Cada uno de ellos es predominante en diferentes regiones de temperatura. A temperaturas bajas y/o cercanas a la transición magnética, la absorción de dipolos paramagnéticos es dominante. A altas temperaturas los dipolos eléctricos, con considerable excitación térmica, dominan la absorción de microondas.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract In this work, we report the profile of non-resonant power absorption of microwaves as a function of temperature; Experimentally named MAMMAS (Magnetically Modulated Microwave Absorption Spectroscopy). The working frequencies is 8.8-9.8 GHz (X-band) on powder samples of ferroelectric BaTiO3 (BT) and PbTiO3 (PT), and magnetoferroelectric YMnO3 (YM) and Pb(Fe1/2Nb1/2)O3 (PFN). MAMMAS profile on ceramic samples BT and PT is due to processes of microwaves absorption associated with electric dipoles. MAMMAS profile for magnetoferroelectrics YM and PFN detect the para-antiferromagnetic transition, and only for the PFN we detect the ferro-paraelectric transition. In the MAMMAS profile it is possible to distinguish processes of absorption associated to electric dipoles or magnetic dipoles. Each one of them is predominant at different regions of temperature. At low temperatures and/or near the magnetic transition, the absorption of paramagnetic dipoles is dominant. At high temperatures the electric dipoles, with considerable thermal excitation, dominates the microwaves absorption.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[Cerámicos]]></kwd>
<kwd lng="es"><![CDATA[Resonancia paramagnética electrónica]]></kwd>
<kwd lng="es"><![CDATA[Ferroeléctricos]]></kwd>
<kwd lng="es"><![CDATA[Magnetoferroeléctricos]]></kwd>
<kwd lng="es"><![CDATA[Transiciones de fase]]></kwd>
<kwd lng="en"><![CDATA[Ceramics]]></kwd>
<kwd lng="en"><![CDATA[Electron paramagnetic resonance]]></kwd>
<kwd lng="en"><![CDATA[Ferroelectrics]]></kwd>
<kwd lng="en"><![CDATA[Magnetoferroelectrics]]></kwd>
<kwd lng="en"><![CDATA[Phase Transitions]]></kwd>
</kwd-group>
</article-meta>
</front><back>
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